The use of high-resolution satellite topographic data to quantify volcanic activity at Raung volcano (Indonesia) from 2011 to 2021

The use of high-resolution satellite topographic data to quantify volcanic activity at Raung volcano (Indonesia) from 2011 to 2021 | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The use of high-resolution satellite topographic data to quantify volcanic activity at Raung volcano (Indonesia) from 2011 to 2021 Federico Galetto, Diego Lobos Lillo, Matthew Pritchard This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4364766/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 02 Dec, 2024 Read the published version in Bulletin of Volcanology → Version 1 posted 5 You are reading this latest preprint version Abstract Quantifying erupted masses of magma is fundamental to determine the size of eruptions. Pre- and post- eruptive Digital Elevation Models (DEMs) derived from satellite data can quantify erupted masses, even in remote areas. Here we used bistatic Synthetic Aperture Radar (SAR) data from the TanDEM-X satellite and EarthDEMs derived by stereo-optical data, to investigate topographic changes and the erupted mass at the caldera of Raung (Indonesia), which is one of the most frequently erupting volcanoes on Java. We found that erupted masses associated with Magnitude ≤ 2 eruptions occurred from 2000 to mid-2014 are difficult to be estimated with these DEMs, due to the difficultly to separate the signal of the limited amount of ash deposited within the caldera from data errors. On the contrary, these DEMs mapped at high resolution deposits of Magnitude ≥ 3 eruptions. The November 2014 – August 2015 eruption produced 11.72 ± 1.58 x10 10 kg of magma (Magnitude 4.06 ± 0.06), generating lava flows with a maximum height of ~ 46–50 meters and a new intra-caldera cone. The January-April 2021 eruption, never studied before, erupted at least 2.29 ± 0.76 x10 10 kg of magma (Magnitude 3.34 ± 0.15), generating lava flows (maximum thickness ~ 16–21 meters) and the growth of the intra-caldera cone. Our analysis reveals that the different pre-eruptive DEMs used to process SAR data and calculate topographic and volume changes can affect extrusive mass estimates by up to ~ 60%. Erupted masses at Raung here estimated could be used in future studies to develop physics-based models coupling extrusion rates with other monitoring parameters to further improve the knowledge of this frequently erupting volcano. Raung volcano volcano topography change remote sensing volcano geodesy erupted masses Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1- Introduction Volcanoes are dynamic systems that can quickly vary their topography over years (De Beni et al. 2015; Eiden et al. 2023). Topographic changes related to the emplacement of erupted products are of particular importance for volcanology, since the erupted mass, or volume, of magma provides the size of eruptions (Pyle 2015; Galetto et al. 2023). Direct field estimations of erupted masses are complicated both by the remote location of many volcanoes and by the difficulty to estimate the height of the erupted products over the entire area covered by volcanic deposits (Kubanek et al. 2015a; De Beni et al. 2019). Erupted masses, especially if associated with effusive activity, can also be estimated by differentiating pre- and post-eruptive high resolution digital elevation models (DEMs) obtained from data acquired with different remote sensing techniques, such as photogrammetry techniques, including Unmanned Aerial Vehicles (UAVs), and Synthetic Aperture Radar Interferometry (InSAR) (Diefenbach et al. 2012, 2013; Poland 2014; Kubanek et al. 2015a; Bagnardi et al. 2016; Kubanek et al. 2017; De Beni et al. 2019; James et al. 2020). (Poland 2014; Kubanek et al. 2015a, 2017). Optical data can be affected by clouds, but they can be used to retrieve high-resolution DEMs in cloud-free areas (Bagnardi et al. 2016). InSAR has the advantage of acquiring data during all weather and during day/night (Kubanek et al. 2017). A great advantage in measuring topographic change from InSAR data comes from SAR satellite missions, like the TanDEM-X mission, that can acquire two images of the same area synchronously, allowing better isolation of the signal due to the topographic change from atmospheric changes, generating more accurate measurements. Remote sensing data are potentially able to generate high-resolution pre- and post- eruptive DEMs at a global scale, providing accurate maps of height changes of volcanic deposits that can be used for precise estimations of erupted volumes (Poland 2014; Bagnardi et al. 2016; Kubanek et al. 2017). These data represent a powerful tool to better constrain the erupted fluxes in poorly monitored volcanoes. For example, Raung volcano (Indonesia) is one of the most frequently erupting, and one of the most dangerous, volcanoes on Java Island, but its erupted masses are poorly constrained, due to the inaccessibility of its caldera floor (Jenkins et al. 2022; Cahyani et al. 2022; Moktikanana and Harijoko 2022; Galetto et al. 2023). Constraining recent erupted masses at Raung would provide, at a local scale, information about the frequency and size distribution of the recent eruptions, while at a regional scale would allow to better constrain the recent regional eruptive rates of Java volcanic arc. In addition, erupted masses of Raung could be used in future studies to develop physics-based models coupling extrusion rates at effusive erupting volcanoes with other monitoring parameters, like deformation and thermal data, to further improve the knowledge of the magmatic system and activity at Raung and to try forecasting its future eruptive rates (Anderson and Segall 2011; Coppola et al. 2023). Thus, here we use DEMs derived from optical and SAR data, acquired from 2011 to 2021, to quantify the erupted masses at Raung volcano, especially during the two effusive eruptions that occurred in November 2014 - August 2015 and January-April 2021. Further, we show the impact of using different reference DEMs, characterized by different spatial resolutions and methods of creation in the processing of InSAR data, to show how they affect the estimated erupted volumes. 2- Geological setting Java Island (Indonesia) is made up by numerous volcanoes, thirty-five of them active during the Holocene (Global Volcanism Program 2013). Its volcanic activity is a direct consequence of the nearly perpendicular subduction of the Indian-Australian oceanic Plate beneath the Eurasian Plate at a rate of ~ 6–7 cm/year (Fig. 1 a; Hamilton 1979; Varekamp et al. 1989; Carn and Pyle 2001; Setijadji et al. 2006). Java has been the arc segment among those forming the Sumatra-Java-east Sunda volcanic arc that erupted the highest amount of magma in the most recent (1980–2019) time (Galetto et al. 2023). One of the most active, but least studied, volcanoes on Java is Raung, placed in the easternmost part of the island. Raung is a stratovolcano, belonging to the volcanic group around the large Ijen caldera (Fig. 1 b; Newhall and Dzurisin 1988), with a ~ 2.2x1.7 km wide summit elliptical caldera, whose major axis is NE-SW oriented, containing an intra-caldera cone in the NE part of the caldera floor. About 49 confirmed eruptions have been recorded since 1902 at Raung (Global Volcanism Program, 2013). Table 1 and Fig. 2 summarize the volcanic activity at Raung from 2000 to 2022 (Global Volcanism Program, 2013) that has been explosive until 2014, with the emission of small ash plumes, classified by the Smithsonian Global Volcanism Program (GVP) with a Volcano Explosivity Index (VEI; Newhall and Self 1982) between 1 and 2 (Table 1 ). Then, Raung underwent a change in its volcanic activity in late 2014, when a strombolian activity produced abundant lavas (Kaneko et al. 2018, 2019). Based on high-resolution satellite data, Kaneko et al., (2019) divided the November 2014 – August 2015 eruption in four stages and estimated a total erupted volume of ~ 7.5 x10 7 m 3 . After a small explosive eruption in 2020 (Table 1 ), another eruption, producing both ash and lava flow, occurred from January to April 2021 (Table 1 ). These two eruptions were preceded by some inflation of the volcano (Kriswati et al. 2021). Table 1 Summary of the volcanic activity at Raung volcano from 2000 to 2022. Data and Descriptions from Global Volcanism Program (2013). VEI = Volcanic Explosivity Index. Dates VEI Description 2022 May 14–2022 Sep 27 2 Explosive. Ash emission 2021 Jan 21–2021 Apr 14 2 Explosive and effusive eruption. Multiple ash plumes observed. A lava flow spread over the NW portion of the caldera. 2020 Jul 16–2020 Oct 3 1 Explosive. Ash emissions 2014 Nov 23 ± 5 days − 2015 Aug 30 ± 8 days 2 Explosive and effusive eruptions (Strombolian activity). Multiple ash plumes observed. Lava spread all over the caldera area. Build of a new cone. [2014 Jan 4–2014 Jan 4] Uncertain Eruption 2013 Jun 29–2013 Jul 31 1 Minor Strombolian activity at the inner crater 2012 Oct 16 ± 2 days − 2013 Jan 6 1 Ash plume and incandescent ejecta observed 2008 Jun 12–2008 Jun 17 (?) 2 Explosive. Ash emission 2007 Jul 26–2007 Aug 26 2 Explosive. Ash emission [2005 Jul 23 (?) − 2005 Aug 15 (?)] Uncertain Eruption [2004 Apr 15 (?) − 2004 Oct 8 (?)] Uncertain Eruption 2002 Jun 16 (in or before) ± 15 days − 2002 Aug 25 (in or after) 2 Explosive. Multiple ash emissions. On Aug. 25 the highest plume height observed (~ 9.2 km a.s.l.). 2000 Jul 9–2000 Jul 9 2 Explosive. Ash emission 3- Methodology 3.1 Data analysed in this study. To better understand the volcanic activity at Raung, we used different remote sensing data. First, we investigated (qualitatively) any surface change due to eruptions using Short-Wave Infrared (SWIR; Sentinel-2) and optical (Maxar and Sentinel-2) data, and SAR amplitude data acquired from the TanDEM-X mission (see section 3.2 ) and from Umbra. Then, to quantify topographic changes due to any eruptions, we created the densest possible time series of topography by using different DEMs. A first set of DEMs come from bistatic data of the TanDEM-X mission. A second set of DEMs, also used for the surface change analysis, are provided by two strips from EarthDEM (Porter et al. 2022), derived from optical WorldView-1 image pairs. Finally, DEMs from the NASA Shuttle Radar Topography Mission (SRTM) (Farr et al. 2007) and from the Copernicus mission (European Space Agency) have been used as reference DEMs to calculate the topographic changes (see sections 3.2 and 3.3). 3.2 Bistatic interferograms and height change The TanDEM-X mission has two nearly identical X-band satellites, TerraSAR-X (TSX) and TanDEM-X (TDX), which can acquire data of the same area synchronously, producing bistatic TSX/TDX pairs of data (Kubanek et al. 2015a, 2017, 2021; Krieger et al. 2007; Zink et al. 2021). Contrary to the conventional InSAR, bistatic acquisitions can be used to generate a single pass interferogram that offers the advantage to measure topography at high resolution (Poland 2014; Kubanek et al. 2015b, 2017, 2021). Indeed, the phase change of bistatic interferograms are not affected by deformation, atmospheric and backscattering errors, since the two scenes are acquired at the same time (Kubanek et al. 2015a, b). Thus, the resultant phase of bistatic interferograms ( ϕ ) can be simplified with respect to the commonly used formula for repeat-pass interferometry as (Kubanek et al. 2015a, b): $$\varphi =W\left\{{\varphi }_{ref}+{\varphi }_{topo}+{\varphi }_{or}+{\varphi }_{N}\right\}$$ 1 Where ϕ ref is the phase attributable to the reference surface, which can be eliminated from a reference DEM; ϕ topo is the target of this analysis and represents the contribution due to deviations of the topography from the reference surface; ϕ or is the residual phase due to orbit errors. Satellite orbits for TSX and TDX satellites have an accuracy often better than 10 cm and therefore ϕ or is negligible for these data (Kubanek et al. 2021). ϕ N is the phase noise. W{⋅} is an operator that drops whole phase cycles (known as “wrapping”), as only the fractional part of the phase can actually be measured (Hooper et al., 2012). To quantify topographic changes, we processed 9 bistatic pairs, 4 from the descending orbit 149 acquired from 2011 to 2013, and 5 from the ascending orbit 111 acquired from 2013 to 2021 (Fig. 2 ). Bistatic interferograms were formed with a modified module of the stripmapApp processor of the InSAR Scientific Computing Environment (ISCE) software (Rosen et al. 2012), which allowed us to co-register the two bistatic SAR data, to generate the interferogram and to remove the contribution of the reference topography ( ϕ ref in Eq. 1 ) by using a reference DEM (see section 3.3). To reduce the noise contribution to the phase ( ϕ N in Eq. 1 ), we applied the adaptive Goldstein-Werner filter (Goldstein and Werner 1998). We unwrapped the bistatic interferograms with the Statistical Network Approach to Phase Unwrapping-Minimum Cost Flow (SNAPHU) algorithm (Chen and Zebker 2001), with the exception of data processed with the EarthDEM for which we used the Integrated Correlation and Unwrapping (ICU) algorithm (Goldstein et al. 1988) to overcome unwrapping errors obtained with SNAPHU (see also Text S1). We converted the unwrapped interferometric phase ( ϕ unwr ) to ground surface height change ( h ) with Eq. 2, valid for bistatic data (Krieger et al. 2013; Kubanek et al. 2015b): $$h=-\frac{\lambda R\text{sin}\vartheta }{2\pi {B}_{\perp }}{\varphi }_{unwr} \left(2\right)$$ Where λ is the radar wavelength (3.1 cm), R is the slant range distance, ϑ is the incidence angle and B ⊥ is the perpendicular baseline (these and other InSAR parameters in Table S1 ). Finally, we geocoded the data to pass from radar to geographic coordinates. 3.3 Reference DEMs To process bistatic interferograms, we use a reference DEM with respect to which we calculate the topographic height change ( h ). The choice of the DEM directly impacts the spatial resolution of the resulting data, since DEMs usually have a worse spatial resolution than bistatic TSX/TDX data. To investigate the impact of the reference DEM on results, we used three different DEMs: 1) The SRTM DEM, acquired in February 2000, which offers a pre-eruptive surface for all our bistatic pairs data (Fig. 2 ). 2) The Copernicus DEM, which is derived from multiple data acquired by the TanDEM-X mission between 2011 and 2015. The comparison between the Copernicus DEM and the SRTM DEM (Figure S1 ) reveals that the Copernicus DEM has been generated from data acquired before the November 2014-August 2015 eruption, providing a good and updated reference surface with respect to which calculate the topographic changes due to the November 2014-August 2015 and the 2021 eruptions. For this reason, we used this DEM as a reference DEM only for the data acquired after the November 2014 eruption (Fig. 2 ). The comparison between the Copernicus and the SRTM DEMs (Figure S1 ) also reveals some differences, with the Copernicus DEM characterized by a smooth topography within the caldera floor, while the SRTM DEM is characterized by a noisy and rough topography, also affected by important changes in values from one pixel to another that might represent errors. Since the topography of the Copernicus DEM is the geoid height referred to the Earth Gravitational Model 2008 (EGM2008), while SAR bistatic TSX/TDX data are referred to the ellipsoidal vertical datum (World Geodetic System 1984; WGS84), we reprojected the Copernicus DEM to convert it from being referred to the geoid to be referred to the ellipsoid by using gdalwarp . We checked the goodness of reprojection by using the SRTM DEM that is provided by NASA in two versions: one referred to the geoid and the other one referred to the ellipsoid. 3) A third set of reference DEMs are provided by two strips from EarthDEM, one acquired on 26 August 2014 and the other one on 28 April 2018 (Fig. 2 ). EarthDEMs have a spatial resolution of 2 m/pixel, while SRTM and Copernicus DEMs have a spatial resolution of ~ 30 m/pixel. Thus, while with the SRTM and Copernicus DEMs, the bistatic TSX/TDX pairs (3 m/pixel) data are resampled to the lower spatial resolution of these DEMs during the processing, we downsampled the EarthDEMs to the same resolution of the bistatic TSX/TDX pairs. The two EarthDEMs have also been differenced to directly calculate the volume erupted during the November 2014 - August 2015 eruption. 4- Results 4.1- Surface change at Raung volcano We use remote sensing data from optical and SWIR satellites (Fig. 3 ) together with SAR amplitude data and EarthDEMs (Fig. 4 ) for a qualitative investigation of surface changes at Raung over time. No surface change was detected at Raung from 2011 to February 2012 (Figure S2 a-c), as expected in a period with no volcanic eruptions (Fig. 2 ). Optical data acquired in March 2011 and in July 2013 show that the intra-caldera cone became filled by new ash in this time span (Fig. 3 a,b; Global Volcanism Program, 2013), likely as a consequence of the October 2012 – January 2013 and the June – July 2013 eruptions (Fig. 2 ). SAR data acquired on 7 January 2013, the day after the end of the October 2012 -January 2013 eruption (Table 1 ), also shows a filling of the intra-caldera cone of Raung (Fig. 4 a-b), revealing that this cone started filling with the October 2012-January 2013 eruption. This filling is also confirmed by data acquired successively (Figs. 3 b, 4 c, Figure S2 e). The EarthDEM acquired in August 2014 (Fig. 4 d) shows a caldera topography characterized by some roughness in the north sector of the caldera and an intra-caldera cone with higher elevation in the east sector, as also suggested by optical and SAR amplitude data (Fig. 3 b, 4 a-c; Figure S2 a-f). The EarthDEM acquired after the November 2014-August 2015 eruption shows a lava flow that spreads all over the caldera floor and a change in the morphology of the intra-caldera cone (Fig. 4 e), confirmed by optical and SAR amplitude data acquired after this eruption (Figs. 3 c-d, 4 f, Figure S2 g-h). Further details about the sin-eruptive surface change of the November 2014-August 2015 eruption are reported in Kaneko et al. (2019). Figure 3 e shows the main explosive paroxysm that occurred on 9 February, of the January-April 2021 eruption, which was followed by lava flow emplacement in the north sector of the caldera (Figs. 3 f-h, 4 g). This eruption also produced a change in the morphology of the intra-caldera cone (Figures, 3g-h, 4g). We used spotlight SAR data acquired in 2023 by Umbra satellite (spatial resolution < 30 cm) to better outline the extension of this lava flow from amplitude data (Fig. 4 h-i). These data also reveal the surface morphology of the 2021 lava flow, characterized by an undulating surface of lava flow lobes, especially in the central and west zone, with the undulations that are particularly accentuated in the central lobe (Figures S3 -4). This morphology suggests a pahoehoe lava flow (Harris and Rowland 2015). Channels are also visible in the lava flow (Figures S3 -4). 4.2- Topographic changes 4.2.1 Pre-November 2014 eruption results Height change from bistatic data acquired before the November 2014-August 2015 eruption have been calculated with respect to the SRTM DEM, acquired before all these data, and the EarthDEM acquired in August 2014, thus after these data, but before the November 2014-August 2015 eruption (Fig. 2 ). Negative height changes in the data processed with the 2014 EarthDEM point a higher topography of this DEM with respect to the bistatic data. All descending and ascending data processed with the SRTM DEM show a negative height change (SE-NW oriented) in the west portion of the caldera (Fig. 5 a-d,i,j). These height changes are related to a putative topographic high reported in this area by the SRTM DEM that seems to no longer exist at the time of acquisition of the bistatic pairs, the Copernicus DEM and the EarthDEM (Figures S1 , S5; see section 6.1 ). Small positive height changes in the NE sector of the intra-caldera cone are also shown in all the data processed with the SRTM DEM (Fig. 5 a-d,i,j; Figure S5 -6). Descending orbit data processed with the 2014 EarthDEM show no significant height changes in most of the caldera area. The only height change obtained from these data is a negative height change in the east flank of the intra-caldera cone (Fig. 5 e-h). This negative height change is not present in the ascending data acquired in 2014 (Fig. 5 k), close to the time of acquisition of the EarthDEM. Descending orbit data acquired in 2012 and in 2013 and ascending orbit data acquired in 2014 show noisy pixels and loss of coherence, when processed with the EarthDEM (Figures S5 d-f, S6e). 4.2.2 November 2014-August 2015 eruptions. The two bistatic data acquired in 2019, thus after the 2014–2015 eruption and before the occurrence of the 2020 and 2021 eruptions (Fig. 2 ), show an important height change in the whole area of the caldera of Raung (Figs. 6 , 7 ). The height change measured with respect to the SRTM DEM is systematically lower than that calculated with respect to the Copernicus DEM and to the 2014 EarthDEM (Figs. 6 – 7 ). In detail, by using a SRTM DEM as reference, we measure a height change due to lava flows emplacement of about 20–26 m both in the SW and in the NW sectors of the caldera (Fig. 6 a,b and 7 a-c), while ~ 12–19 m of height change occurred in the NE sector, characterized by a higher pre-eruptive topography (Figs. 6 a-b, 7 a-c). The maximum height changes (~ 30–44 m) are measured at the base of the intra-caldera cone (Fig. 6 b). By using a Copernicus DEM as reference, we obtain height changes of 42–46, 32–42 and ~ 15–38 m in the SW, NW and NE sectors of the caldera, respectively (Figs. 6 c-d, 7 d-f). The highest height changes (~ 70–81 m) have been recorded in the coherent pixels placed in the S area of the intra-caldera cone (Fig. 6 d). However, both data processed with the SRTM and the Copernicus DEMs have low coherence in the intra-caldera cone, generating an overall loss of information in this area (Fig. 6 a-d). Height changes calculated with respect to the EarthDEM acquired in 2014 show 43–50, 35–43 and 17–38 m of height change in the SW, NW and NE sectors, respectively (Figs. 6 e-f, 7 g-i), similar to those obtained from the Copernicus DEM. In the intra-caldera cone, these data record ~ 100–110 and 120–138 m of height change in the SW and E-SE sectors of the cone, respectively. Finally, as an independent check on the height changes measured from bistatic pairs data, we calculated the height changes by differentiating the EarthDEMs acquired in April 2018 and in August 2014 (Fig. 6 g). Results show height changes of 46–50, 35–44 and 20–37 m in the SW, NW and NE sectors, respectively (Fig. 7 g-i). The maximum height changes (~ 90–95 m) are from the SE sector of the intra-caldera cone. 4.2.3 The January-April 2021 eruption. Since both SRTM and Copernicus DEMs have been acquired before the November 2014 – August 2015 eruption, the height change calculated from the bistatic pair data acquired in July 2021 with respect to these reference DEMs contains the information associated with both the 2014–2015 and the 2021 eruptions (Figure S7 ). To remove the contribution of the 2014–2015 eruption, we calculated the difference between the height changes obtained from the 2021 bistatic data and the height changes from bistatic pairs data acquired in 2019, processed with the same DEMs to remove the common background (unchanged) topography (Fig. 8 a-d). Data processed with SRTM shows an increase in the height change with respect to data acquired in 2019 of ~ 5–9 m in the north sector of the caldera (NW, N and NE), where the 2021 lava flow was emplaced. Maximum height changes of ~ 20–28 m are recorded in the NE cone (Figs. 7 a-c, 8 a-b). Data processed with the Copernicus DEM show an heigh change of ~ 12–16 m in the NW and N sector of the caldera, with the highest values (~ 16 meters) recorded immediately to the west of the intra-caldera cone. Height changes of ~ 9–13 meters have been obtained in the NE sector. The intra-caldera cone is characterized by an overall loss of coherence and of information, with the few pixels covering it that show a height change of ~ 15–25 m (Figs. 7 d-f, 8 c-d). Finally, the 2021 bistatic pair data processed with the EarthDEM acquired in 2018 shows height change of ~ 14–19 meters in the N and NW sectors of the caldera and maximum values of ~ 21 m in the area adjacent to the W sector of the intra-caldera cone. Height change of ~ 10–16 m characterize the NE sector of the caldera. As for the intra-caldera cone, our data maintain coherence in the S and W flanks of the cone (from the base to almost up to the summit), with positive height change of ~ 100–124 m (Figs. 7 g-i, 8 e; see section 6 ). 5- Volume estimation and associated uncertainties. We calculated uncertainties in the height change using the approach in Poland (2014) and Kubanek et al., (2017). We selected reference areas outside the caldera of Raung not affected by topographic changes and we calculated the mean value (that ideally should be zero) and the standard deviation (that provides us the uncertainty in the height change) of all pixels within the selected reference areas (Table 2 ). Further details on how we estimated errors and on the choice of the reference areas are reported in Text S2 and in Figures S8 -18. The height change errors in Table 2 have been used to quantify the erupted volumes errors (Table 3 ). We associated lower errors in Table 2 , usually calculated in flat areas (see Text S2), to pixels covering the caldera area, since this is a relatively flat area with no vegetation, while we associated the higher errors in Table 2 , calculated along steep flanks (see Text S2), to the intra-caldera cone, characterized by steeper topography (Tables S2-S3). The only exception is for the 2021 bistatic data processed with the 2018 EarthDEM, which had no flat areas where to estimate errors (see Text S2), and therefore we associated errors estimated in the steep flanks to all pixels. Table 2 Statistical parameters (Mean = mean value; Std = standard deviation) calculated in reference areas (Figures S8 -18) of the bistatic pair interferograms that should not have been affected by height changes. In bold italics is reported the DEM used to process the data. For the definition of Zone a and Zone b see Figure S16. (*) Height changes of the bistatic data acquired from 2014 to 2019 have been calculated with respect to the 2014 EarthDEM, while those from the data acquired in 2021 have been calculated with respect to the 2018 EarthDEM. Descending orbit data Flat area outside the volcano Steep and/or highly vegetated area SRTM Mean (m) Std (m) Mean (m) Std (m) 3 Feb. 2011 -0.527 1.028 -0.761 6.256 26 Jun. 2011 -0.717 0.832 -1.113 3.790 23 Feb. 2012 0.181 0.866 -0.091 4.276 7 Jan. 2013 -0.168 0.730 -1.750 4.258 Ascending orbit data Flat area outside the volcano Steep and/or highly vegetated area Copernicus Mean (m) Std (m) Mean (m) Std (m) 3 Jan. 2019 -0.510 1.098 1.467 5.258 10 Dec. 2019 -0.583 1.094 1.744 4.445 15 Jul. 2021 -1.305 1.078 2.865 5.083 SRTM 26 Sep. 2013 0.287 0.600 -0.673 1.773 27 Feb. 2014 -0.006 0.430 -0.604 1.744 3 Jan. 2019 -0.217 0.479 0.305 2.529 10 Dec. 2019 0.181 0.685 -0.035 2.094 15 Jul. 2021 -0.105 0.666 0.805 2.213 EarthDEM (*) 27 Feb. 2014 2.440 2.777 0.441 7.658 3 Jan. 2019 0.714 2.524 -0.240 4.274 10 Dec. 2019 1.648 2.655 -1.675 7.254 15 Jul. 2021 No data 0.926 4.605 Difference between the 2018 and the 2014 EarthDEMs Zone a No data -3.947 4.745 Zone b No data -4.187 6.240 We estimated the erupted bulk volumes from pixels with positive height change (Table 3 ). For the pre-November 2014 bistatic pair data processed with the 2014 EarthDEM, we used the negative pixels, because the 2014 EarthDEM has been acquired after these data (Fig. 2 ) and therefore negative pixels point an increase in topography (Table 3 ; Table S2 ). Since our bistatic data do not maintain coherence in the whole area of the caldera, we report the area covered by our data (Tables S2 and S4). In addition, for bistatic pairs acquired in 2019 and 2021, we were able to quantify the percentage of the area covered by coherent pixels of our data with respect to the whole area covered by volcanic products of the November 2014-August 2015 and the 2021 eruptions, estimated from the 2018 EarthDEM and from data in Fig. 3 g (Table 3 ; Table S4 ). As for the 2021 eruption, we removed from volume calculation those pixels covering the S and the SW area of the caldera, which have not been affected by the deposition of new products during this eruption (Figure S19). The volume change obtained by removing these pixels (Table 3 ) is, however, very similar to that obtained maintaining them (Table S5 ). The VEI scale fails in quantifying the size of effusive eruptions, since it considers only the explosive products (Newhall and Self 1982; Pyle 2015; Galetto et al. 2023). Thus, we used the Magnitude scale, which is a logarithmic scale able to quantify the size of eruptions regardless the nature of their products, defined by Eq. 3 (Pyle 2015): $$Magnitude={\text{log}}_{10}\left(erupted mass in kg\right)-7 \left(3\right)$$ To estimate the size of the analysed eruptions, we converted the bulk volume, estimated from the height change, in Dense Rock Equivalent (DRE) volume and in erupted mass (Table 3 ). According to Kaneko et al. (2019), we separated for the November 2014-August 2015 and the 2021 eruptions the area of the intra-caldera cone from the caldera area covered by lava flows (Tables S2-3), since the vesicularity of products making up the cone is usually greater than that of lava flows (e.g., Harris and Rowland 2015). However, the vesicularity and composition of these products is unknown (Kaneko et al., 2019), thus we assumed a density of 1000 kg/m 3 (Kaneko et al., 2019) to convert the bulk volume of the cone in mass and a density of 2750 kg/m 3 , typical of basalts (Stolper and Walker 1980; Rose et al. 2008; Bonadonna et al. 2022), for the DRE volume. As for lavas covering the caldera area, we assumed a vesicularity of 25% to convert the bulk volume in DRE volume (Poland 2014; Bagnardi et al. 2016) and a density of 2750 kg/m 3 to convert the DRE volume in mass. The choice of a DRE density typical of basalts has been assumed since Raung usually erupts basaltic lavas (Moktikanana and Harijoko 2022). Furthermore, the pahoehoe surface of the 2021 lavas (Figures S3 -4) is more typical of basaltic magmas, although sometimes felsic magmas can assume this morphology when they flow over flat surface (Harris and Rowland 2015). Basaltic composition was also hypothesized by Kaneko et al., (2019) for the 2014–2015 eruption, based on the lava flows morphology and for the occurrence of a lava lake during this eruption. For bistatic data acquired before November 2014, we converted the bulk volume in erupted mass assuming a density of 1000 kg/m 3 , since eruptions covered by these data were explosive (Table 1 ). Table 3 Erupted volumes during different eruptive episodes using different reference DEMs: SRTM, Copernicus and EarthDEM compared to bistatic data. 2018 EarthDEM − 2014 EarthDEM are values obtained from subtracting the 2018 EarthDEM to the 2014 EarthDEM. V = bulk volume. % A/A_er is the percental ratio between the caldera area covered by data (negative and positive values) and the caldera area affected by the eruption. This ratio quantifies how much of the caldera area with new volcano deposits is covered by our data. See Table S4 for exact values of A and A_er. V DRE is the total erupted volume in DRE, while M is the total erupted mass (see Section 5 for details). For bistatic data acquired before November 2014, values in square brackets represent the lower and upper bounds of the bulk volume and of the mass. V (x10 6 m 3 ) M (x10 9 kg) Pre-November 2014 data SRTM 3 Feb. 2011 (desc.) 1.40 [0.54 3.05] 1.40 [0.54 3.05] 26 Jun. 2011 (desc.) 1.56 [0.79 2.73] 1.56 [0.79 2.73] 23 Feb. 2012 (desc.) 1.97 [1.20 3.17] 1.97 [1.20 3.17] 7 Jan. 2013 (desc.) 1.88 [1.10 3.03] 1.88 [1.10 3.03] 23 Sep. 2013 (asc.) 2.12 [1.24 3.14] 2.12 [1.24 3.14] 27 Feb. 2014 (asc.) 1.34 [0.77 2.07] 1.34 [0.77 2.07] 2014 EarthDEM 3 Feb. 2011 (desc.) 0.28 0.28 26 Jun. 2011 (desc.) 1.12 1.12 23 Feb. 2012 (desc.) 2.24 2.24 7 Jan. 2013 (desc.) 1.03 1.03 27 Feb. 2014 (asc.) 3.43 [0.56 7.91] 3.43 [0.56 7.91] V (x10 6 m 3 ) % A/A_er V DRE (x10 6 m 3 ) M (x10 10 kg) 2014–2015 eruption SRTM 3 Jan. 2019 (asc.) (25.45 ± 1.04) 80.76 (18.26 ± 0.60) (5.02 ± 0.17) 10 Dec. 2019 (asc.) (25.61 ± 1.18) 80.39 (18.28 ± 0.76) (5.03 ± 0.21) Copernicus 3 Jan. 2019 (asc.) (43.91 ± 1.71) 75.15 (32.37 ± 1.14) (8.90 ± 0.31) 10 Dec. 2019 (asc.) (47.30 ± 1.80) 78.11 (34.59 ± 1.18) (9.51 ± 0.33) 2014 EarthDEM 3 Jan. 2019 (asc.) (42 ± 3.12) 70.48 (30.23 ± 2.20) (8.31 ± 0.60) 10 Dec. 2019 (asc.) (43.90 ± 3.73) 72.86 (31.48 ± 2.52) (8.66 ± 0.69) 2018 EarthDEM − 2014 EarthDEM 2018 − 2014 (EarthDEMs) (61.24 ± 8.38) 100 (42.62 ± 5.75) (11.72 ± 1.58) 2021 eruption (only pixels in the area covered by volcanic deposits associated to the 2021 eruption reported in Figure S19) SRTM 3 Jan. 2019–15 Jul. 2021 (asc.) (5.24 ± 0.78) 72.6 (3.56 ± 0.49) (0.98 ± 0.13) 10 Dec. 2019–15 Jul. 2021 (asc.) (4.97 ± 0.72) 70.36 (3.49 ± 0.47) (0.96 ± 0.13) Copernicus 3 Jan. 2019–15 Jul. 2021 (asc.) (9.69 ± 1.17) 70.01 (7.07 ± 0.78) (1.95 ± 0.21) 10 Dec. 2019–15 Jul. 2021 (asc.) (8.44 ± 1.17) 70.92 (6.19 ± 0.78) (1.70 ± 0.21) 2018 EarthDEM 15 Jul. 2021 (asc.) (11.96 ± 3.95) 70.74 (8.34 ± 2.78) (2.29 ± 0.76) 6- Discussion 6.1 Height changes and the impact of the reference DEM used. Bistatic pairs acquired before the November 2014 eruption show no significant topographic changes, with agreement among all the reference DEMs (Figures S5 -6). One exception is that all data compared to the SRTM DEM have a negative height change (NW-SE oriented) in the western sector of the caldera (Fig. 5 a-d,i-j), but there are no field data that allow us to understand if it might be a true anomaly, possibly due to a landslide occurred before 2011 (date of the first bistatic pair; Fig. 2 ), or if it is only a result of an error in the SRTM DEM. Some small positive height changes recorded immediately to the E of this negative height change might support the landslide theory, representing the accumulation area of the deposits. Positive and negative height changes, with respect to all the reference DEMs used, recorded along the steep flank of the intra-caldera cone seem more related to a different estimate of the steepness of the cone recorded by the bistatic data with respect to that of the reference DEMs than to true height changes, as shown by elevation profiles (Figures S5 -6). However, we cannot exclude that some height changes in Fig. 5 are related to the small explosive eruptions that occurred between the time of acquisition of the reference DEMs and the bistatic data, especially for the data processed with the SRTM (Fig. 2 ). If all positive height changes of data processed with the SRTM were related to eruptive products, and not to errors in the DEM, the total erupted bulk volume would be of 0.54–3.17 x10 6 m 3 (Table 3 ), equal to a magnitude 1.79–2.5, which is also consistent with the VEI 1–2 assigned by the GVP to explosive eruptions that occurred between the acquisition of the SRTM and of the bistatic data. Descending orbit data acquired from June 2011 to 2013 and ascending orbit data acquired in 2014 show a low signal-to-noise ratio in the caldera area when processed with the 2014 EarthDEM (Fig. 5 f-h,k and Figures S5 d-f, S6d-f), suggesting that these bistatic pairs are noisier in the caldera area than the others. This also affects the volume change estimation, with the volume change estimated for the February 2014 bistatic data that is different than zero (Table 3 ), although no eruption occurred between the acquisition of this data and that of the 2014 EarthDEM (Fig. 2 ). This hints that errors in the caldera could be sometimes larger than the error estimated in the reference areas outside the caldera. Similarly, also volumes estimated by the noisy data acquired from June 2011 to 2013 and processed with the 2014 EarthDEM (Table 3 ) might be overestimated due to the low signal-to-noise ratio of these data. It is interesting to note that the same noisy ascending and descending data are less noisy when processed with the SRTM DEM, possibly due to the larger pixels size (30 m instead of the 3 m resolution of the bistatic data) that is each pixel value is an average of 100 pixels of the bistatic data, with positive and negative noisy pixels likely cancelling each other during the averaging. The lack of coherence in the SW area of the caldera in the bistatic pair acquired on 7 January 2013 (Fig. 5 h), processed with the 2014 EarthDEM, is possibly also related to the eruption that ended the day before the acquisition of this data. Bistatic pairs data acquired in 2019 allowed us to constrain the height changes associated with the November 2014-August 2015 eruption. Data processed with the SRTM DEM show lower (up to the 40–50% in the caldera floor and up to the 45–68% in the cone) height changes than those obtained from the same data processed with the other reference DEMs and with respect to those obtained by differencing the 2014 and the 2018 EarthDEMs (Fig. 6 ). Thus, the erupted volumes estimated from the bistatic data processed with the SRTM DEM are of ~ 40–59% lower than that estimated from the same data processed with the other reference DEMs (Table 3 ). Therefore, in this case the use of the SRTM DEM as the reference DEM leads to an erroneous calculation of the height changes and of the erupted volumes. This is possibly due to the high roughness of the SRTM topography in the S and W sector of the caldera floor (Figure S1 ), which are also the sectors where height changes were most underestimated within the caldera floor (Figs. 6 – 7 ). On the contrary, bistatic pairs data processed with the Copernicus and the 2014 EarthDEM show height changes within the caldera floor that are consistent both with each other and with those calculated from differentiating the 2018 and the 2014 EarthDEMs. In addition, height changes in the caldera floor from these DEMs are also consistent with those inferred by Kaneko et al. (2019) using different sets of high-resolution satellite images. In the area of the intra-caldera cone we observe an overall lack of information, especially in data processed with the Copernicus DEM (Fig. 6 ). The loss of coherence can be related to both the high gradient of height change in the cone and to factors causing geometric decorrelation in steep areas, like shadows and layover effects (Kubanek et al., 2015b). Coherent pixels of bistatic data processed with the Copernicus and the 2014 EarthDEM DEMs in the intra-caldera cone show a small shift in the position of both the flanks and the summit of the intra-caldera cone with respect to the geometry recorded by the 2018 EarthDEM (e.g., Fig. 7 g,h). This shift could be related to small errors in the geocoding of the bistatic data, or to small errors in the position of the cone in the 2018 EarthDEM. Bistatic data processed with the 2014 EarthDEM show higher height changes (up to 138 meters) at the top and in the SW flank of the intra-caldera cone with respect to those retrieved from differentiating the 2018 and the 2014 EarthDEMs (Figs. 6 , 7 ). This implies that the 2019 bistatic pairs record a higher height of the cone formed during the 2014–2015 eruption than the 2018 EarthDEM. The height recorded by the bistatic data is consistent with the maximum height of the cone (~ 143 m) inferred by Kaneko et al. (2019). The bistatic pair data acquired in July 2021 provide us the opportunity to infer the height change and the associated erupted volume after the November 2014 - August 2015 eruption. Two eruptions occurred after the 2015 and before the date of acquisition of the July 2021 bistatic data (Table 1 , Fig. 2 ): a small explosive eruption in 2020 and a larger explosive to effusive eruption in January-April 2021. Since the height changes recorded by our data match well with the location of the 2021 lava flows and the associated new intra-caldera cone (Figs. 3 f-h, 4 g-i, 8 ), here we assume that all the height changes recorded by the 2021 bistatic data are related to the January-April 2021 eruption. As with the 2014–2015 eruptions, height changes in the caldera floor area from the 2021 eruptions obtained from the difference of the bistatic data processed with the SRTM DEM are ~ 44–64% lower than those estimated from data processed with the Copernicus DEM and with the 2018 EarthDEM (Fig. 8 and Figure S19). The bistatic pairs data processed with the 2018 EarthDEM shows also much higher height changes (up to 124m) in the intra-caldera cone with respect to the data processed with SRTM DEM, while data processed with the Copernicus DEM are incoherent in this area. 6.2 Magnitude of the eruptions We estimated from differencing the 2018 and the 2014 EarthDEMs a bulk volume of 61.24 ± 8.38 x10 6 m 3 of magma erupted during the November 2014 – August 2015 eruption, which corresponds to a DRE volume of 42.62 ± 5.75 x10 6 m 3 and to a mass of 11.72 ± 1.58 x10 10 kg of magma (Table 3 ), equal to a Magnitude 4.06 ± 0.06 eruption. Volumes and masses estimated from bistatic pairs data acquired in 2019 and processed with the Copernicus and the 2014 EarthDEM are ~ 19–31% lower (Table 3 ), but this discrepancy is explained by the fact that these data do not maintain coherence in ~ 20–30% of the caldera area covered by volcanic products of this eruption, especially in the cone area (Table 3 and Table S4 ). Kaneko et al. (2019) estimated a volume of 74.8 ± 11.2 x10 6 m 3 for this eruption, but they converted the volume of the cone in DRE assuming a lava density of 2500 kg/m 3 and pyroclastic material density of 1000 kg/m 3 and they did not correct the volume of lavas emplaced in the caldera floor for vesicularity. With the same assumptions, we would obtain a volume of 56.1 ± 7.54 x10 6 m 3 , still quite consistent with that from Kaneko et al. (2019), although the volume of the intra-caldera cone estimated by these authors do not come directly from data as in our case, but was assumed to be equivalent to that of a conical solid having a height of 143 m and a basal planar radius of 279 m at which they subtracted the volume of the pre-eruptive cone assumed equal to a cone having a height of 35 m and a basal planar radius of 279 m. As for the January-April 2021 eruption, volumes and masses estimated from data processed with the SRTM are ~ 41–64% lower than that estimated from data processed with the 2018 EarthDEM and with the Copernicus DEM (Table 3 ). The Magnitude associated to data processed with the Copernicus DEM and with the 2018 EarthDEM ranges from 3.2 to 3.5. However, also in this case, data do not maintain coherence in ~ 30% of the caldera area covered by volcanic products of this eruption (Table 3 ), especially in the zone of the intra-caldera cone. Data processed with the 2018 EarthDEM shows a maximum height change in the cone of ~ 124 meters and therefore the lack of data in ~ 64–85% of the cone (Table S4 ) can generate an important underestimation of the total volume, also considering that lavas in the caldera floor have a lower height and cover a lower surface than lavas of the 2014–2015 eruption and, therefore, have less impact on the total volume of the 2021 eruption. To have an idea of the amount of the volume underestimated due to the lack of coherence, we used two different approaches. First, we interpolated the 2021 bistatic data processed with the 2018 EarthDEM, which is the only DEM that maintains some coherence in the intra-caldera cone (Figure S20 and Table S6 ). We are aware that the interpolation in the cone area is not correct from a theoretical point of view, due to the lack of data in the east and central portion of the cone (Fig. 8 e) that potentially leads to large interpolation errors in this area, but at least it provides a raw value of the potential volume lost by incoherent pixels. Second, we assume a conical geometry of the intra-caldera cone, with a radius of 280 meters and a maximum height of 124 meters (from the bistatic data processed with the 2018 EarthDEM), and we calculated the associated volume (Table S6 ). Although these estimations should not be considered exact values of the volume of the cone, they hint that the bulk volume of the cone might be 73–98% higher than that estimated from our analysis. The magnitude of the eruption would pass from 3.36 (estimated from the 2021 bistatic data processed with the 2018 EarthDEM; Table 3 ) to 3.44–3.50 (Table S6 ) and from 3.23–3.29 to 3.35–3.46 by extrapolating values of the cone in Table S6 to the data processed with the Copernicus DEM. As expected for effusive eruptions, the Magnitude we estimated for the November 2015 – August 2015 and for the January-July 2021 (4.06 ± 0.06 and 3.36 ± 0.14 respectively) is higher than the VEI 2 assigned by the Smithsonian Global Volcanism Program to these eruptions, with important implication in the recent eruptive rates of this volcano. Furthermore, it is important to note that volumes and masses estimated in our analysis refer only to volcanic products deposited within the caldera of Raung, while an unknown mass of ash associated to the volcanic plumes of these eruptions (e.g. Figure 3 e) has been carried away by winds and deposited outside the caldera. 7- Conclusions We used high-resolution DEMs derived from SAR bistatic data and optical EarthDEMs to investigate the eruptive activity at Raung volcano. We found that the reference DEM used to process bistatic data can significantly affect the estimation of height changes and volumes, especially if the DEM is characterized by a noisy rough pre-eruptive topography, as the case of the SRTM DEM. On the contrary, despite their different spatial resolutions (30m vs. 3m), data processed with the Copernicus DEM are consistent with that processed at full resolution with the EarthDEMs, although these latter data maintain better coherence in steep areas, such as those of the intra-caldera cone. However, areas with steep slopes, like that of the cone, in all the bistatic data experience at least a partial loss of coherence and information, regardless the reference DEM used. This is likely also due to factors causing geometric decorrelation of bistatic data in steep areas, like shadows and layover effects, limiting the applicability of DEM derived by these data to calculate the topographic changes over the entire steep slopes. Our results show that DEMs acquired before the November 2014 eruption are characterized by small height changes where it is difficult to separate true signals from errors. Thus, volume change connected to Magnitude 2, or smaller, explosive eruptions, as those occurred before November 2014, are difficult to calculate from these data. On the other hand, these data can be used to map at high resolution the topographic changes due to Magnitude ≥ 3 eruption and to calculate the erupted volumes from them. With these data we determine a DRE volume of 42.62 ± 5.75 x10 6 m 3 for volcanic products deposited within the caldera of Raung during the November 204 - August 2015 eruption, quite consistent with that estimated by Kaneko et al. (2019) (see section 6.2 ). A minimum DRE volume of 8.34 ± 2.78 x10 6 m 3 has been estimated for volcanic deposits within the caldera of Raung associated to the January-April 2021 eruption, but our data do not maintain coherence in the whole area of the caldera covered by deposits of this eruption (especially in the cone), potentially missing a 16–27% of the DRE erupted volume. Our analysis reveals that after many years (at least from 2000 to October 2014; Fig. 2 ) characterized by mild explosive volcanic activity, with only tephra emission, Raung experienced a Magnitude ≥ 4 and a Magnitude > 3.0 eruption in seven years, with the production of lavas. Time series of high resolution DEMs derived from satellite data provide therefore a powerful tool to quantify masses erupted by Magnitude ≥ 3 eruptions, which can be used in future studies to develop physics-based models coupling extrusion rates with other monitoring parameters, like deformation and thermal data, to further improve the knowledge of the magmatic systems and the volcanic activity at Raung and to try forecasting its future eruptive rates (Anderson and Segall 2011; Coppola et al. 2023). Declarations Competing interests : we declare to do not have financial interests that are directly or indirectly related to this work. Acknowledgments F. Galetto and M. E. Pritchard were supported by 80NSSC21K0842 issued through NASA’s Science Mission Directorate’s Earth Science Division, which also provided the access to the bistatic TSX/TDX data. Data availability Copernicus DEM ( https://doi.org/10.5270/ESA-c5d3d65 ) is open source and is freely available at https://portal.opentopography.org/raster?opentopoID=OTSDEM.032021.4326.3 . The NASA SRTM DEM is open source and is freely available at https://earthexplorer.usgs.gov/ or at https://portal.opentopography.org/raster?opentopoID=OTSRTM.082016.4326.1 . Strip EarthDEM (Porter et al. 2022) is available to U.S. federal employees/contractors and federally-funded researchers. Maxar data in Fig. 3 comes from GoogleEarth pro, while Sentinel data are freely available are freely provided through the Copernicus Program of the European Union ( https://dataspace.copernicus.eu/browser/ ). 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IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 14:3546–3565. https://doi.org/10.1109/JSTARS.2021.3062286 Supplementary Files SupplemenatryTableS1.xlsx SupplemenatryTableS2.xlsx SupplemenatryTableS3.xlsx SupplemenatryTableS4.xlsx SupplemenatryTableS5.xlsx SupplemenatryTableS6.xlsx SupplementaryFigures.pdf SupplementaryText.docx Cite Share Download PDF Status: Published Journal Publication published 02 Dec, 2024 Read the published version in Bulletin of Volcanology → Version 1 posted Editorial decision: Moderate revision (possibly re-reviewed) 10 Sep, 2024 Reviewers agreed at journal 03 Jun, 2024 Reviewers invited by journal 02 Jun, 2024 Editor invited by journal 20 May, 2024 First submitted to journal 06 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4364766","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":309636062,"identity":"acfb8c68-878f-49c8-a183-8ba3de90f88d","order_by":0,"name":"Federico Galetto","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYBAC9gbm4x8/VIDZjAceAIkGQlp4DrClMUucgXAOJBCnhceMgbeNJC38C8weSM6zkzOf3XwAqMVGdsMBQlokHqQbFG5LNpa5cywBqCXNmKAWe4kDByQktx1InCGRYwDUcjiRCFsONkjwzgFpyf8A1PKfCC38zWwSvA1gW0DeP0CMLWzMxhLHko0lJNKADjNINp5J2JbzHx9+qLGTk5BIfvjgQ4WdbB8hLQwSCcg8A0LKQYCfoKGjYBSMglEw4gEA4chH5dL9PgYAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-9469-3968","institution":"Cornell University","correspondingAuthor":true,"prefix":"","firstName":"Federico","middleName":"","lastName":"Galetto","suffix":""},{"id":309636063,"identity":"7803f98a-3f9b-4766-b4e2-7d035d5b6377","order_by":1,"name":"Diego Lobos Lillo","email":"","orcid":"","institution":"Cornell University","correspondingAuthor":false,"prefix":"","firstName":"Diego","middleName":"Lobos","lastName":"Lillo","suffix":""},{"id":309636064,"identity":"491568e4-871b-48c2-924f-4fa177e36676","order_by":2,"name":"Matthew Pritchard","email":"","orcid":"","institution":"Cornell University","correspondingAuthor":false,"prefix":"","firstName":"Matthew","middleName":"","lastName":"Pritchard","suffix":""}],"badges":[],"createdAt":"2024-05-03 14:47:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4364766/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4364766/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00445-024-01781-1","type":"published","date":"2024-12-02T15:57:39+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":58378887,"identity":"ec572875-434e-49fd-b11e-dcf3b7c4b202","added_by":"auto","created_at":"2024-06-14 16:05:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1620975,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ea) Geological and tectonic setting of Indonesia. The black square points the location of Panel b. Plate boundaries from Bird 2003, with the black hachures showing the relative motion at convergent plate boundaries. b) Copernicus DEM hill shade (\u003c/em\u003e\u003ca href=\"https://doi.org/10.5270/ESA-c5d3d65\"\u003ehttps://doi.org/10.5270/ESA-c5d3d65\u003c/a\u003e) \u003cem\u003eof the Volcanic Group of Ijen Caldera with Raung placed in the SW of this group. The red square shows the area in Figure 3.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/9e7c6a1bfceb2409c801c166.png"},{"id":58378612,"identity":"a8d39b1e-5572-4c9f-b218-37e38c58ef78","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":43759,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eEruptive periods of Raung (red lines and rectangles; Table 1, Global Volcanism Program 2013) and the acquisition times of remote sensing data and DEMs used in this work. As for the Copernicus DEM (COP), we report the time interval of the mission, since this DEM comes from the interpolation of multiple data acquired over the specified time span. Bistatic pairs are the bistatic pairs of the TanDEM-X satellite (asc.=ascending orbit; desc.=descending orbit). Letters in brackets below the purple triangles are referred to the panels of Figure 3 where these data are shown.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/e5bad3384030c15467fac0bc.png"},{"id":58378886,"identity":"1aa385b4-43a3-44e5-990e-231409ad9c60","added_by":"auto","created_at":"2024-06-14 16:05:35","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":5434924,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ea-b) Maxar data (from GoogleEarth pro) acquired before the November 2014 eruption. Panel b shows the filling of the intra-caldera crater with volcanic ash. c-d) Post November 2014-August 2015 eruption Maxar images showing the new lava flow in the whole caldera area and the new intra-caldera cone. e-f) Short-Wave Infrared (SWIR) (R=band 12; G=band 11; B=band 4) Sentinel 2B (panel e) and Sentinel 2A (panels f) images acquired during the January - April 2021 eruption. g-h) Sentinel-2A image (panel g) and Maxar image (panel h) acquired after the January - April 2021 eruption, showing the new lava flow in the north and west sector of the caldera and the new cone morphology. See Figure 2 for the acquisition time of these data (purple triangles) with respect to the eruptive periods of Raung.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/9d0c5227a27dc78d111ed99d.png"},{"id":58378613,"identity":"d2f43a5f-2b6b-4eea-994a-56caa5d691d7","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":3016911,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ea-c,f-g) Selected TanDEM-X SAR amplitude data from descending (a-b) and ascending (c,f,g) orbits. See Figure S2 for the other TanDEM-X amplitude data covering the period 2011-2019. Data are in radar coordinates (descending data have been reflected vertically, while ascending data have been reflected horizontally to be consistent each other). Different geometric distortions and shadows between ascending and descending data are related to the different side-looking geometry of the radar beam. d-e) EarthDEMs acquired in 2014 (d) and in 2018 (e). h-i) Umbra (Um.) spotlight SAR amplitude data (right and left looking observation directions for data in panel h and i, respectively). Umbra data are Geocoded Ellipsoid Corrected (GEC) products (SAR amplitude data geocoded and projected onto the WGS84 ellipsoid by the vendor). Yellow and orange dashed lines in panels e-i show the extent of the lava flow erupted in the 2014-2015 eruption (e-f) and in the 2021 eruption (g-i). See Figure 2 for the acquisition time of these data with respect to the eruptions occurred at Raung.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/7aa3298a5da715ddcf1d9558.png"},{"id":58379147,"identity":"08119a14-c2fb-4be7-9301-ec421f941102","added_by":"auto","created_at":"2024-06-14 16:13:35","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2478995,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003ea-h) Descending orbit data for Raung from 2011 to 2013. The height change is calculated with respect to the SRTM DEM (a-d) and the EarthDEM acquired in August 2014 (e-h). i-k) Ascending orbit data from 2013 to 2014. The height change is with respect to the SRTM DEM (i-j) and the 2014 EarthDEM (k). All data are plotted above the 2014 EarthDEM hill-shade topography. See Figure 2 for the time acquisition of these data with respect to the eruptive periods.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/111231a94b81b31d195f98e8.png"},{"id":58378618,"identity":"a71f74e9-61e2-4208-b32e-85d53dbbb567","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2374798,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eHeight change at Raung due to the November 2014- August 2015 eruption calculated with respect to the SRTM DEM (a-b), the Copernicus DEM (c-d) and the EarthDEM acquired in August 2014 (e-f). g) Height change obtained by subtracting the EarthDEM acquired in April 2018 to the EarthDEM acquired in August 2014. Data in panels (a-g) are plotted above the 2018 EarthDEM hill-shade topography. h) Tracks of the topographic profiles in Figure 7 plotted on the 2014 EarthDEM.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/40e0cf5bf34b6f88890007d9.png"},{"id":58378883,"identity":"10276916-fd27-4693-ae89-44929ae5c197","added_by":"auto","created_at":"2024-06-14 16:05:35","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":104367,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eTopographic profiles, whose tracks are reported in Figure 6h. a-c) Topographic profiles referred to data in Figure 6a,b. d-f) Topographic profiles referred to data in Figure 6c-d. g-i) Topographic profiles referred to data in Figure 6e-g. 2014 EarthDEM, SRTM and Copernicus (COP) DEMs represent the pre-eruptive topography that existed before the November 2014 – August 2015 eruption (Figure 2). Heights are referred to the ellipsoidal vertical datum WGS84.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/fc19ddaddbe916c30280c34d.png"},{"id":58378614,"identity":"43426773-59ae-4021-8fa9-3c8542012899","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":2313145,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eHeight change at Raung from bistatic data acquired in July 2021. Data have been processed with the SRTM DEM (a-b), the Copernicus DEM (c-d) and with the EarthDEM acquired in April 2018 (e), respectively. Data in panels a-d have been obtained from the difference between the height changes obtained from the 2021 bistatic data and the height changes from bistatic data acquired in 2019, processed with the same DEM to remove the common background (unchanged) topography. All data are plotted above a Sentinel-2A image acquired on 14 July 2021.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/05d49b64e7341ec8f7c31938.png"},{"id":70965292,"identity":"218e0127-f7af-4931-b67d-0990c753bfd3","added_by":"auto","created_at":"2024-12-09 16:18:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":20458259,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/56fbf3c9-f073-43d0-8063-f79e0f49cd43.pdf"},{"id":58378617,"identity":"44a7d287-9ef4-4472-bc18-ca0b9200e66d","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"xlsx","order_by":12,"title":"","display":"","copyAsset":false,"role":"supplement","size":14059,"visible":true,"origin":"","legend":"","description":"","filename":"SupplemenatryTableS1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/547a8644e1fe13a33c95c209.xlsx"},{"id":58378623,"identity":"b121ae51-7ffa-4156-9f05-32f871eb1e9b","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"xlsx","order_by":13,"title":"","display":"","copyAsset":false,"role":"supplement","size":15206,"visible":true,"origin":"","legend":"","description":"","filename":"SupplemenatryTableS2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/fa39d42409aadc9e9644c8ba.xlsx"},{"id":58378624,"identity":"8067ed09-8044-4a38-b869-73f23ec7a93b","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"xlsx","order_by":14,"title":"","display":"","copyAsset":false,"role":"supplement","size":16957,"visible":true,"origin":"","legend":"","description":"","filename":"SupplemenatryTableS3.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/0a3d033e7f603590c555f990.xlsx"},{"id":58378626,"identity":"37464d86-e210-49c2-b2da-5790a8228414","added_by":"auto","created_at":"2024-06-14 15:57:36","extension":"xlsx","order_by":15,"title":"","display":"","copyAsset":false,"role":"supplement","size":15893,"visible":true,"origin":"","legend":"","description":"","filename":"SupplemenatryTableS4.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/1dcae10f2b4a7ccad16d0a15.xlsx"},{"id":58378621,"identity":"12ed609d-00b1-4a8e-a2e6-3655c9009361","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"xlsx","order_by":16,"title":"","display":"","copyAsset":false,"role":"supplement","size":12851,"visible":true,"origin":"","legend":"","description":"","filename":"SupplemenatryTableS5.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/e0abecbfe1599007ac265781.xlsx"},{"id":58378620,"identity":"bd29aff1-fe85-47b6-a6c6-c8865bdf8a19","added_by":"auto","created_at":"2024-06-14 15:57:35","extension":"xlsx","order_by":17,"title":"","display":"","copyAsset":false,"role":"supplement","size":12884,"visible":true,"origin":"","legend":"","description":"","filename":"SupplemenatryTableS6.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/99a6731423ca5580a3ca6f73.xlsx"},{"id":58378628,"identity":"a94744ec-d6db-4c74-9766-1121d51cb76c","added_by":"auto","created_at":"2024-06-14 15:57:36","extension":"pdf","order_by":18,"title":"","display":"","copyAsset":false,"role":"supplement","size":5386269,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryFigures.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/c8ca92c0483708497ed740b5.pdf"},{"id":58378885,"identity":"b4317d29-aca4-46c4-a791-d24cbae082ee","added_by":"auto","created_at":"2024-06-14 16:05:35","extension":"docx","order_by":19,"title":"","display":"","copyAsset":false,"role":"supplement","size":17242,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryText.docx","url":"https://assets-eu.researchsquare.com/files/rs-4364766/v1/dd11024bc4d4661af4ce744b.docx"}],"financialInterests":"","formattedTitle":"The use of high-resolution satellite topographic data to quantify volcanic activity at Raung volcano (Indonesia) from 2011 to 2021","fulltext":[{"header":"1- Introduction","content":"\u003cp\u003eVolcanoes are dynamic systems that can quickly vary their topography over years (De Beni et al. 2015; Eiden et al. 2023). Topographic changes related to the emplacement of erupted products are of particular importance for volcanology, since the erupted mass, or volume, of magma provides the size of eruptions (Pyle 2015; Galetto et al. 2023). Direct field estimations of erupted masses are complicated both by the remote location of many volcanoes and by the difficulty to estimate the height of the erupted products over the entire area covered by volcanic deposits (Kubanek et al. 2015a; De Beni et al. 2019). Erupted masses, especially if associated with effusive activity, can also be estimated by differentiating pre- and post-eruptive high resolution digital elevation models (DEMs) obtained from data acquired with different remote sensing techniques, such as photogrammetry techniques, including Unmanned Aerial Vehicles (UAVs), and Synthetic Aperture Radar Interferometry (InSAR) (Diefenbach et al. 2012, 2013; Poland 2014; Kubanek et al. 2015a; Bagnardi et al. 2016; Kubanek et al. 2017; De Beni et al. 2019; James et al. 2020). (Poland 2014; Kubanek et al. 2015a, 2017). Optical data can be affected by clouds, but they can be used to retrieve high-resolution DEMs in cloud-free areas (Bagnardi et al. 2016). InSAR has the advantage of acquiring data during all weather and during day/night (Kubanek et al. 2017). A great advantage in measuring topographic change from InSAR data comes from SAR satellite missions, like the TanDEM-X mission, that can acquire two images of the same area synchronously, allowing better isolation of the signal due to the topographic change from atmospheric changes, generating more accurate measurements.\u003c/p\u003e \u003cp\u003eRemote sensing data are potentially able to generate high-resolution pre- and post- eruptive DEMs at a global scale, providing accurate maps of height changes of volcanic deposits that can be used for precise estimations of erupted volumes (Poland 2014; Bagnardi et al. 2016; Kubanek et al. 2017). These data represent a powerful tool to better constrain the erupted fluxes in poorly monitored volcanoes. For example, Raung volcano (Indonesia) is one of the most frequently erupting, and one of the most dangerous, volcanoes on Java Island, but its erupted masses are poorly constrained, due to the inaccessibility of its caldera floor (Jenkins et al. 2022; Cahyani et al. 2022; Moktikanana and Harijoko 2022; Galetto et al. 2023). Constraining recent erupted masses at Raung would provide, at a local scale, information about the frequency and size distribution of the recent eruptions, while at a regional scale would allow to better constrain the recent regional eruptive rates of Java volcanic arc. In addition, erupted masses of Raung could be used in future studies to develop physics-based models coupling extrusion rates at effusive erupting volcanoes with other monitoring parameters, like deformation and thermal data, to further improve the knowledge of the magmatic system and activity at Raung and to try forecasting its future eruptive rates (Anderson and Segall 2011; Coppola et al. 2023). Thus, here we use DEMs derived from optical and SAR data, acquired from 2011 to 2021, to quantify the erupted masses at Raung volcano, especially during the two effusive eruptions that occurred in November 2014 - August 2015 and January-April 2021. Further, we show the impact of using different reference DEMs, characterized by different spatial resolutions and methods of creation in the processing of InSAR data, to show how they affect the estimated erupted volumes.\u003c/p\u003e"},{"header":"2- Geological setting","content":"\u003cp\u003eJava Island (Indonesia) is made up by numerous volcanoes, thirty-five of them active during the Holocene (Global Volcanism Program 2013). Its volcanic activity is a direct consequence of the nearly perpendicular subduction of the Indian-Australian oceanic Plate beneath the Eurasian Plate at a rate of ~\u0026thinsp;6\u0026ndash;7 cm/year (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea; Hamilton 1979; Varekamp et al. 1989; Carn and Pyle 2001; Setijadji et al. 2006). Java has been the arc segment among those forming the Sumatra-Java-east Sunda volcanic arc that erupted the highest amount of magma in the most recent (1980\u0026ndash;2019) time (Galetto et al. 2023). One of the most active, but least studied, volcanoes on Java is Raung, placed in the easternmost part of the island. Raung is a stratovolcano, belonging to the volcanic group around the large Ijen caldera (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb; Newhall and Dzurisin 1988), with a\u0026thinsp;~\u0026thinsp;2.2x1.7 km wide summit elliptical caldera, whose major axis is NE-SW oriented, containing an intra-caldera cone in the NE part of the caldera floor. About 49 confirmed eruptions have been recorded since 1902 at Raung (Global Volcanism Program, 2013). Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e summarize the volcanic activity at Raung from 2000 to 2022 (Global Volcanism Program, 2013) that has been explosive until 2014, with the emission of small ash plumes, classified by the Smithsonian Global Volcanism Program (GVP) with a Volcano Explosivity Index (VEI; Newhall and Self 1982) between 1 and 2 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Then, Raung underwent a change in its volcanic activity in late 2014, when a strombolian activity produced abundant lavas (Kaneko et al. 2018, 2019). Based on high-resolution satellite data, Kaneko et al., (2019) divided the November 2014 \u0026ndash; August 2015 eruption in four stages and estimated a total erupted volume of ~\u0026thinsp;7.5 x10\u003csup\u003e7\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e. After a small explosive eruption in 2020 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), another eruption, producing both ash and lava flow, occurred from January to April 2021 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These two eruptions were preceded by some inflation of the volcano (Kriswati et al. 2021).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of the volcanic activity at Raung volcano from 2000 to 2022. Data and Descriptions from Global Volcanism Program (2013). VEI\u0026thinsp;=\u0026thinsp;Volcanic Explosivity Index.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDates\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVEI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDescription\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2022 May 14\u0026ndash;2022 Sep 27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExplosive. Ash emission\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2021 Jan 21\u0026ndash;2021 Apr 14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExplosive and effusive eruption. Multiple ash plumes observed. A lava flow spread over the NW portion of the caldera.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2020 Jul 16\u0026ndash;2020 Oct 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExplosive. Ash emissions\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2014 Nov 23\u0026thinsp;\u0026plusmn;\u0026thinsp;5 days \u0026minus;\u0026thinsp;2015 Aug 30\u0026thinsp;\u0026plusmn;\u0026thinsp;8 days\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExplosive and effusive eruptions (Strombolian activity). Multiple ash plumes observed. Lava spread all over the caldera area. Build of a new cone.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[2014 Jan 4\u0026ndash;2014 Jan 4]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eUncertain Eruption\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2013 Jun 29\u0026ndash;2013 Jul 31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMinor Strombolian activity at the inner crater\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2012 Oct 16\u0026thinsp;\u0026plusmn;\u0026thinsp;2 days \u0026minus;\u0026thinsp;2013 Jan 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAsh plume and incandescent ejecta observed\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2008 Jun 12\u0026ndash;2008 Jun 17 (?)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExplosive. Ash emission\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2007 Jul 26\u0026ndash;2007 Aug 26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExplosive. Ash emission\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[2005 Jul 23 (?) \u0026minus;\u0026thinsp;2005 Aug 15 (?)]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eUncertain Eruption\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e[2004 Apr 15 (?) \u0026minus;\u0026thinsp;2004 Oct 8 (?)]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eUncertain Eruption\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2002 Jun 16 (in or before)\u0026thinsp;\u0026plusmn;\u0026thinsp;15 days \u0026minus;\u0026thinsp;2002 Aug 25 (in or after)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExplosive. Multiple ash emissions. On Aug. 25 the highest plume height observed (~\u0026thinsp;9.2 km a.s.l.).\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2000 Jul 9\u0026ndash;2000 Jul 9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eExplosive. Ash emission\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"3- Methodology","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Data analysed in this study.\u003c/h2\u003e \u003cp\u003eTo better understand the volcanic activity at Raung, we used different remote sensing data. First, we investigated (qualitatively) any surface change due to eruptions using Short-Wave Infrared (SWIR; Sentinel-2) and optical (Maxar and Sentinel-2) data, and SAR amplitude data acquired from the TanDEM-X mission (see section \u003cspan refid=\"Sec5\" class=\"InternalRef\"\u003e3.2\u003c/span\u003e) and from Umbra. Then, to quantify topographic changes due to any eruptions, we created the densest possible time series of topography by using different DEMs. A first set of DEMs come from bistatic data of the TanDEM-X mission. A second set of DEMs, also used for the surface change analysis, are provided by two strips from EarthDEM (Porter et al. 2022), derived from optical WorldView-1 image pairs. Finally, DEMs from the NASA Shuttle Radar Topography Mission (SRTM) (Farr et al. 2007) and from the Copernicus mission (European Space Agency) have been used as reference DEMs to calculate the topographic changes (see sections \u003cspan refid=\"Sec5\" class=\"InternalRef\"\u003e3.2\u003c/span\u003e and 3.3).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Bistatic interferograms and height change\u003c/h2\u003e \u003cp\u003eThe TanDEM-X mission has two nearly identical X-band satellites, TerraSAR-X (TSX) and TanDEM-X (TDX), which can acquire data of the same area synchronously, producing bistatic TSX/TDX pairs of data (Kubanek et al. 2015a, 2017, 2021; Krieger et al. 2007; Zink et al. 2021). Contrary to the conventional InSAR, bistatic acquisitions can be used to generate a single pass interferogram that offers the advantage to measure topography at high resolution (Poland 2014; Kubanek et al. 2015b, 2017, 2021). Indeed, the phase change of bistatic interferograms are not affected by deformation, atmospheric and backscattering errors, since the two scenes are acquired at the same time (Kubanek et al. 2015a, b). Thus, the resultant phase of bistatic interferograms (\u003cem\u003eϕ\u003c/em\u003e) can be simplified with respect to the commonly used formula for repeat-pass interferometry as (Kubanek et al. 2015a, b):\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\varphi =W\\left\\{{\\varphi }_{ref}+{\\varphi }_{topo}+{\\varphi }_{or}+{\\varphi }_{N}\\right\\}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere \u003cem\u003eϕ\u003c/em\u003e\u003csub\u003e\u003cem\u003eref\u003c/em\u003e\u003c/sub\u003e is the phase attributable to the reference surface, which can be eliminated from a reference DEM; \u003cem\u003eϕ\u003c/em\u003e\u003csub\u003e\u003cem\u003etopo\u003c/em\u003e\u003c/sub\u003e is the target of this analysis and represents the contribution due to deviations of the topography from the reference surface; \u003cem\u003eϕ\u003c/em\u003e\u003csub\u003e\u003cem\u003eor\u003c/em\u003e\u003c/sub\u003e is the residual phase due to orbit errors. Satellite orbits for TSX and TDX satellites have an accuracy often better than 10 cm and therefore \u003cem\u003eϕ\u003c/em\u003e\u003csub\u003e\u003cem\u003eor\u003c/em\u003e\u003c/sub\u003e is negligible for these data (Kubanek et al. 2021). \u003cem\u003eϕ\u003c/em\u003e\u003csub\u003e\u003cem\u003eN\u003c/em\u003e\u003c/sub\u003e is the phase noise. W{\u0026sdot;} is an operator that drops whole phase cycles (known as \u0026ldquo;wrapping\u0026rdquo;), as only the fractional part of the phase can actually be measured (Hooper et al., 2012).\u003c/p\u003e \u003cp\u003eTo quantify topographic changes, we processed 9 bistatic pairs, 4 from the descending orbit 149 acquired from 2011 to 2013, and 5 from the ascending orbit 111 acquired from 2013 to 2021 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Bistatic interferograms were formed with a modified module of the \u003cem\u003estripmapApp\u003c/em\u003e processor of the InSAR Scientific Computing Environment (ISCE) software (Rosen et al. 2012), which allowed us to co-register the two bistatic SAR data, to generate the interferogram and to remove the contribution of the reference topography (\u003cem\u003eϕ\u003c/em\u003e\u003csub\u003e\u003cem\u003eref\u003c/em\u003e\u003c/sub\u003e in Eq.\u0026nbsp;\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) by using a reference DEM (see section 3.3). To reduce the noise contribution to the phase (\u003cem\u003eϕ\u003c/em\u003e\u003csub\u003e\u003cem\u003eN\u003c/em\u003e\u003c/sub\u003e in Eq.\u0026nbsp;\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), we applied the adaptive Goldstein-Werner filter (Goldstein and Werner 1998). We unwrapped the bistatic interferograms with the Statistical Network Approach to Phase Unwrapping-Minimum Cost Flow (SNAPHU) algorithm (Chen and Zebker 2001), with the exception of data processed with the EarthDEM for which we used the Integrated Correlation and Unwrapping (ICU) algorithm (Goldstein et al. 1988) to overcome unwrapping errors obtained with SNAPHU (see also Text S1). We converted the unwrapped interferometric phase (\u003cem\u003eϕ\u003c/em\u003e\u003csub\u003e\u003cem\u003eunwr\u003c/em\u003e\u003c/sub\u003e) to ground surface height change (\u003cem\u003eh\u003c/em\u003e) with Eq.\u0026nbsp;2, valid for bistatic data (Krieger et al. 2013; Kubanek et al. 2015b):\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$h=-\\frac{\\lambda R\\text{sin}\\vartheta }{2\\pi {B}_{\\perp }}{\\varphi }_{unwr} \\left(2\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere λ is the radar wavelength (3.1 cm), R is the slant range distance, ϑ is the incidence angle and \u003cem\u003eB\u003c/em\u003e\u003csub\u003e\u003cem\u003e\u0026perp;\u003c/em\u003e\u003c/sub\u003e is the perpendicular baseline (these and other InSAR parameters in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFinally, we geocoded the data to pass from radar to geographic coordinates.\u003c/p\u003e \u003cp\u003e \u003cem\u003e3.3 Reference DEMs\u003c/em\u003e \u003c/p\u003e \u003cp\u003eTo process bistatic interferograms, we use a reference DEM with respect to which we calculate the topographic height change (\u003cem\u003eh\u003c/em\u003e). The choice of the DEM directly impacts the spatial resolution of the resulting data, since DEMs usually have a worse spatial resolution than bistatic TSX/TDX data. To investigate the impact of the reference DEM on results, we used three different DEMs:\u003c/p\u003e \u003cp\u003e1) The SRTM DEM, acquired in February 2000, which offers a pre-eruptive surface for all our bistatic pairs data (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e2) The Copernicus DEM, which is derived from multiple data acquired by the TanDEM-X mission between 2011 and 2015. The comparison between the Copernicus DEM and the SRTM DEM (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e) reveals that the Copernicus DEM has been generated from data acquired before the November 2014-August 2015 eruption, providing a good and updated reference surface with respect to which calculate the topographic changes due to the November 2014-August 2015 and the 2021 eruptions. For this reason, we used this DEM as a reference DEM only for the data acquired after the November 2014 eruption (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The comparison between the Copernicus and the SRTM DEMs (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e) also reveals some differences, with the Copernicus DEM characterized by a smooth topography within the caldera floor, while the SRTM DEM is characterized by a noisy and rough topography, also affected by important changes in values from one pixel to another that might represent errors. Since the topography of the Copernicus DEM is the geoid height referred to the Earth Gravitational Model 2008 (EGM2008), while SAR bistatic TSX/TDX data are referred to the ellipsoidal vertical datum (World Geodetic System 1984; WGS84), we reprojected the Copernicus DEM to convert it from being referred to the geoid to be referred to the ellipsoid by using \u003cem\u003egdalwarp\u003c/em\u003e. We checked the goodness of reprojection by using the SRTM DEM that is provided by NASA in two versions: one referred to the geoid and the other one referred to the ellipsoid.\u003c/p\u003e \u003cp\u003e3) A third set of reference DEMs are provided by two strips from EarthDEM, one acquired on 26 August 2014 and the other one on 28 April 2018 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). EarthDEMs have a spatial resolution of 2 m/pixel, while SRTM and Copernicus DEMs have a spatial resolution of ~\u0026thinsp;30 m/pixel. Thus, while with the SRTM and Copernicus DEMs, the bistatic TSX/TDX pairs (3 m/pixel) data are resampled to the lower spatial resolution of these DEMs during the processing, we downsampled the EarthDEMs to the same resolution of the bistatic TSX/TDX pairs. The two EarthDEMs have also been differenced to directly calculate the volume erupted during the November 2014 - August 2015 eruption.\u003c/p\u003e \u003c/div\u003e"},{"header":"4- Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e4.1- Surface change at Raung volcano\u003c/h2\u003e \u003cp\u003eWe use remote sensing data from optical and SWIR satellites (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) together with SAR amplitude data and EarthDEMs (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) for a qualitative investigation of surface changes at Raung over time. No surface change was detected at Raung from 2011 to February 2012 (Figure \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003ea-c), as expected in a period with no volcanic eruptions (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Optical data acquired in March 2011 and in July 2013 show that the intra-caldera cone became filled by new ash in this time span (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea,b; Global Volcanism Program, 2013), likely as a consequence of the October 2012 \u0026ndash; January 2013 and the June \u0026ndash; July 2013 eruptions (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). SAR data acquired on 7 January 2013, the day after the end of the October 2012 -January 2013 eruption (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), also shows a filling of the intra-caldera cone of Raung (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea-b), revealing that this cone started filling with the October 2012-January 2013 eruption. This filling is also confirmed by data acquired successively (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec, Figure \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003ee). The EarthDEM acquired in August 2014 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed) shows a caldera topography characterized by some roughness in the north sector of the caldera and an intra-caldera cone with higher elevation in the east sector, as also suggested by optical and SAR amplitude data (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea-c; Figure \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003ea-f). The EarthDEM acquired after the November 2014-August 2015 eruption shows a lava flow that spreads all over the caldera floor and a change in the morphology of the intra-caldera cone (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee), confirmed by optical and SAR amplitude data acquired after this eruption (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec-d, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef, Figure \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003eg-h). Further details about the sin-eruptive surface change of the November 2014-August 2015 eruption are reported in Kaneko et al. (2019). Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee shows the main explosive paroxysm that occurred on 9 February, of the January-April 2021 eruption, which was followed by lava flow emplacement in the north sector of the caldera (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef-h, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg). This eruption also produced a change in the morphology of the intra-caldera cone (Figures, 3g-h, 4g). We used spotlight SAR data acquired in 2023 by Umbra satellite (spatial resolution\u0026thinsp;\u0026lt;\u0026thinsp;30 cm) to better outline the extension of this lava flow from amplitude data (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh-i). These data also reveal the surface morphology of the 2021 lava flow, characterized by an undulating surface of lava flow lobes, especially in the central and west zone, with the undulations that are particularly accentuated in the central lobe (Figures \u003cspan refid=\"MOESM3\" class=\"InternalRef\"\u003eS3\u003c/span\u003e-4). This morphology suggests a pahoehoe lava flow (Harris and Rowland 2015). Channels are also visible in the lava flow (Figures \u003cspan refid=\"MOESM3\" class=\"InternalRef\"\u003eS3\u003c/span\u003e-4).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e4.2- Topographic changes\u003c/h2\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e4.2.1 Pre-November 2014 eruption results\u003c/h2\u003e \u003cp\u003eHeight change from bistatic data acquired before the November 2014-August 2015 eruption have been calculated with respect to the SRTM DEM, acquired before all these data, and the EarthDEM acquired in August 2014, thus after these data, but before the November 2014-August 2015 eruption (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Negative height changes in the data processed with the 2014 EarthDEM point a higher topography of this DEM with respect to the bistatic data.\u003c/p\u003e \u003cp\u003eAll descending and ascending data processed with the SRTM DEM show a negative height change (SE-NW oriented) in the west portion of the caldera (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea-d,i,j). These height changes are related to a putative topographic high reported in this area by the SRTM DEM that seems to no longer exist at the time of acquisition of the bistatic pairs, the Copernicus DEM and the EarthDEM (Figures \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, S5; see section \u003cspan refid=\"Sec14\" class=\"InternalRef\"\u003e6.1\u003c/span\u003e). Small positive height changes in the NE sector of the intra-caldera cone are also shown in all the data processed with the SRTM DEM (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea-d,i,j; Figure \u003cspan refid=\"MOESM5\" class=\"InternalRef\"\u003eS5\u003c/span\u003e-6). Descending orbit data processed with the 2014 EarthDEM show no significant height changes in most of the caldera area. The only height change obtained from these data is a negative height change in the east flank of the intra-caldera cone (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee-h). This negative height change is not present in the ascending data acquired in 2014 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ek), close to the time of acquisition of the EarthDEM. Descending orbit data acquired in 2012 and in 2013 and ascending orbit data acquired in 2014 show noisy pixels and loss of coherence, when processed with the EarthDEM (Figures \u003cspan refid=\"MOESM5\" class=\"InternalRef\"\u003eS5\u003c/span\u003ed-f, S6e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e4.2.2 November 2014-August 2015 eruptions.\u003c/h2\u003e \u003cp\u003eThe two bistatic data acquired in 2019, thus after the 2014\u0026ndash;2015 eruption and before the occurrence of the 2020 and 2021 eruptions (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), show an important height change in the whole area of the caldera of Raung (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The height change measured with respect to the SRTM DEM is systematically lower than that calculated with respect to the Copernicus DEM and to the 2014 EarthDEM (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). In detail, by using a SRTM DEM as reference, we measure a height change due to lava flows emplacement of about 20\u0026ndash;26 m both in the SW and in the NW sectors of the caldera (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea,b and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea-c), while\u0026thinsp;~\u0026thinsp;12\u0026ndash;19 m of height change occurred in the NE sector, characterized by a higher pre-eruptive topography (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea-b, \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea-c). The maximum height changes (~\u0026thinsp;30\u0026ndash;44 m) are measured at the base of the intra-caldera cone (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb). By using a Copernicus DEM as reference, we obtain height changes of 42\u0026ndash;46, 32\u0026ndash;42 and ~\u0026thinsp;15\u0026ndash;38 m in the SW, NW and NE sectors of the caldera, respectively (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec-d, \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ed-f). The highest height changes (~\u0026thinsp;70\u0026ndash;81 m) have been recorded in the coherent pixels placed in the S area of the intra-caldera cone (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed). However, both data processed with the SRTM and the Copernicus DEMs have low coherence in the intra-caldera cone, generating an overall loss of information in this area (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea-d). Height changes calculated with respect to the EarthDEM acquired in 2014 show 43\u0026ndash;50, 35\u0026ndash;43 and 17\u0026ndash;38 m of height change in the SW, NW and NE sectors, respectively (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee-f, \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eg-i), similar to those obtained from the Copernicus DEM. In the intra-caldera cone, these data record\u0026thinsp;~\u0026thinsp;100\u0026ndash;110 and 120\u0026ndash;138 m of height change in the SW and E-SE sectors of the cone, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFinally, as an independent check on the height changes measured from bistatic pairs data, we calculated the height changes by differentiating the EarthDEMs acquired in April 2018 and in August 2014 (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eg). Results show height changes of 46\u0026ndash;50, 35\u0026ndash;44 and 20\u0026ndash;37 m in the SW, NW and NE sectors, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eg-i). The maximum height changes (~\u0026thinsp;90\u0026ndash;95 m) are from the SE sector of the intra-caldera cone.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e4.2.3 The January-April 2021 eruption.\u003c/h2\u003e \u003cp\u003eSince both SRTM and Copernicus DEMs have been acquired before the November 2014 \u0026ndash; August 2015 eruption, the height change calculated from the bistatic pair data acquired in July 2021 with respect to these reference DEMs contains the information associated with both the 2014\u0026ndash;2015 and the 2021 eruptions (Figure \u003cspan refid=\"MOESM7\" class=\"InternalRef\"\u003eS7\u003c/span\u003e). To remove the contribution of the 2014\u0026ndash;2015 eruption, we calculated the difference between the height changes obtained from the 2021 bistatic data and the height changes from bistatic pairs data acquired in 2019, processed with the same DEMs to remove the common background (unchanged) topography (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea-d). Data processed with SRTM shows an increase in the height change with respect to data acquired in 2019 of ~\u0026thinsp;5\u0026ndash;9 m in the north sector of the caldera (NW, N and NE), where the 2021 lava flow was emplaced. Maximum height changes of ~\u0026thinsp;20\u0026ndash;28 m are recorded in the NE cone (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea-c, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea-b). Data processed with the Copernicus DEM show an heigh change of ~\u0026thinsp;12\u0026ndash;16 m in the NW and N sector of the caldera, with the highest values (~\u0026thinsp;16 meters) recorded immediately to the west of the intra-caldera cone. Height changes of ~\u0026thinsp;9\u0026ndash;13 meters have been obtained in the NE sector. The intra-caldera cone is characterized by an overall loss of coherence and of information, with the few pixels covering it that show a height change of ~\u0026thinsp;15\u0026ndash;25 m (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ed-f, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec-d). Finally, the 2021 bistatic pair data processed with the EarthDEM acquired in 2018 shows height change of ~\u0026thinsp;14\u0026ndash;19 meters in the N and NW sectors of the caldera and maximum values of ~\u0026thinsp;21 m in the area adjacent to the W sector of the intra-caldera cone. Height change of ~\u0026thinsp;10\u0026ndash;16 m characterize the NE sector of the caldera. As for the intra-caldera cone, our data maintain coherence in the S and W flanks of the cone (from the base to almost up to the summit), with positive height change of ~\u0026thinsp;100\u0026ndash;124 m (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eg-i, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ee; see section \u003cspan refid=\"Sec13\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"5- Volume estimation and associated uncertainties.","content":"\u003cp\u003eWe calculated uncertainties in the height change using the approach in Poland (2014) and Kubanek et al., (2017). We selected reference areas outside the caldera of Raung not affected by topographic changes and we calculated the mean value (that ideally should be zero) and the standard deviation (that provides us the uncertainty in the height change) of all pixels within the selected reference areas (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Further details on how we estimated errors and on the choice of the reference areas are reported in Text S2 and in Figures \u003cspan refid=\"MOESM8\" class=\"InternalRef\"\u003eS8\u003c/span\u003e-18. The height change errors in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e have been used to quantify the erupted volumes errors (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). We associated lower errors in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, usually calculated in flat areas (see Text S2), to pixels covering the caldera area, since this is a relatively flat area with no vegetation, while we associated the higher errors in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, calculated along steep flanks (see Text S2), to the intra-caldera cone, characterized by steeper topography (Tables S2-S3). The only exception is for the 2021 bistatic data processed with the 2018 EarthDEM, which had no flat areas where to estimate errors (see Text S2), and therefore we associated errors estimated in the steep flanks to all pixels.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e \u003cem\u003eStatistical parameters (Mean\u0026thinsp;=\u0026thinsp;mean value; Std\u0026thinsp;=\u0026thinsp;standard deviation) calculated in reference areas (Figures \u003cspan refid=\"MOESM8\" class=\"InternalRef\"\u003eS8\u003c/span\u003e-18) of the bistatic pair interferograms that should not have been affected by height changes. In bold italics is reported the DEM used to process the data. For the definition of Zone a and Zone b see Figure S16. (*) Height changes of the bistatic data acquired from 2014 to 2019 have been calculated with respect to the 2014 EarthDEM, while those from the data acquired in 2021 have been calculated with respect to the 2018 EarthDEM.\u003c/em\u003e \u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eDescending orbit data\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e\u003cem\u003eFlat area outside the volcano\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e\u003cem\u003eSteep and/or highly vegetated area\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSRTM\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eMean (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eStd (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eMean (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eStd (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Feb. 2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.527\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.761\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.256\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e26 Jun. 2011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.717\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.832\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-1.113\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.790\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e23 Feb. 2012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.181\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.866\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.091\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.276\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7 Jan. 2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.168\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.730\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-1.750\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.258\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eAscending orbit data\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e\u003cem\u003eFlat area outside the volcano\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e\u003cem\u003eSteep and/or highly vegetated area\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCopernicus\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eMean (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eStd (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eMean (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eStd (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Jan. 2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.510\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.098\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.467\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.258\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10 Dec. 2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.583\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.094\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.744\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.445\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15 Jul. 2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-1.305\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.078\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.865\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.083\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSRTM\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e26 Sep. 2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.287\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.673\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.773\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e27 Feb. 2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.430\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.604\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.744\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Jan. 2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.217\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.479\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.305\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.529\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10 Dec. 2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.181\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.685\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.035\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.094\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15 Jul. 2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.105\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.666\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.805\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.213\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEarthDEM (*)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e27 Feb. 2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.440\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.777\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.441\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.658\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Jan. 2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.714\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.524\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.274\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10 Dec. 2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.648\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.655\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-1.675\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.254\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15 Jul. 2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eNo data\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.926\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.605\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDifference between the 2018 and the 2014 EarthDEMs\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZone a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eNo data\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-3.947\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.745\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZone b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eNo data\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-4.187\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.240\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWe estimated the erupted bulk volumes from pixels with positive height change (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). For the pre-November 2014 bistatic pair data processed with the 2014 EarthDEM, we used the negative pixels, because the 2014 EarthDEM has been acquired after these data (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) and therefore negative pixels point an increase in topography (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e; Table \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e). Since our bistatic data do not maintain coherence in the whole area of the caldera, we report the area covered by our data (Tables S2 and S4). In addition, for bistatic pairs acquired in 2019 and 2021, we were able to quantify the percentage of the area covered by coherent pixels of our data with respect to the whole area covered by volcanic products of the November 2014-August 2015 and the 2021 eruptions, estimated from the 2018 EarthDEM and from data in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e; Table \u003cspan refid=\"MOESM4\" class=\"InternalRef\"\u003eS4\u003c/span\u003e). As for the 2021 eruption, we removed from volume calculation those pixels covering the S and the SW area of the caldera, which have not been affected by the deposition of new products during this eruption (Figure S19). The volume change obtained by removing these pixels (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) is, however, very similar to that obtained maintaining them (Table \u003cspan refid=\"MOESM5\" class=\"InternalRef\"\u003eS5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe VEI scale fails in quantifying the size of effusive eruptions, since it considers only the explosive products (Newhall and Self 1982; Pyle 2015; Galetto et al. 2023). Thus, we used the Magnitude scale, which is a logarithmic scale able to quantify the size of eruptions regardless the nature of their products, defined by Eq.\u0026nbsp;3 (Pyle 2015):\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$Magnitude={\\text{log}}_{10}\\left(erupted mass in kg\\right)-7 \\left(3\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eTo estimate the size of the analysed eruptions, we converted the bulk volume, estimated from the height change, in Dense Rock Equivalent (DRE) volume and in erupted mass (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). According to Kaneko et al. (2019), we separated for the November 2014-August 2015 and the 2021 eruptions the area of the intra-caldera cone from the caldera area covered by lava flows (Tables S2-3), since the vesicularity of products making up the cone is usually greater than that of lava flows (e.g., Harris and Rowland 2015). However, the vesicularity and composition of these products is unknown (Kaneko et al., 2019), thus we assumed a density of 1000 kg/m\u003csup\u003e3\u003c/sup\u003e (Kaneko et al., 2019) to convert the bulk volume of the cone in mass and a density of 2750 kg/m\u003csup\u003e3\u003c/sup\u003e, typical of basalts (Stolper and Walker 1980; Rose et al. 2008; Bonadonna et al. 2022), for the DRE volume. As for lavas covering the caldera area, we assumed a vesicularity of 25% to convert the bulk volume in DRE volume (Poland 2014; Bagnardi et al. 2016) and a density of 2750 kg/m\u003csup\u003e3\u003c/sup\u003e to convert the DRE volume in mass. The choice of a DRE density typical of basalts has been assumed since Raung usually erupts basaltic lavas (Moktikanana and Harijoko 2022). Furthermore, the pahoehoe surface of the 2021 lavas (Figures \u003cspan refid=\"MOESM3\" class=\"InternalRef\"\u003eS3\u003c/span\u003e-4) is more typical of basaltic magmas, although sometimes felsic magmas can assume this morphology when they flow over flat surface (Harris and Rowland 2015). Basaltic composition was also hypothesized by Kaneko et al., (2019) for the 2014\u0026ndash;2015 eruption, based on the lava flows morphology and for the occurrence of a lava lake during this eruption. For bistatic data acquired before November 2014, we converted the bulk volume in erupted mass assuming a density of 1000 kg/m\u003csup\u003e3\u003c/sup\u003e, since eruptions covered by these data were explosive (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e \u003cem\u003eErupted volumes during different eruptive episodes using different reference DEMs: SRTM, Copernicus and EarthDEM compared to bistatic data. 2018 EarthDEM\u003c/em\u003e \u0026minus;\u0026thinsp;\u003cem\u003e2014 EarthDEM are values obtained from subtracting the 2018 EarthDEM to the 2014 EarthDEM. V\u0026thinsp;=\u0026thinsp;bulk volume. % A/A_er is the percental ratio between the caldera area covered by data (negative and positive values) and the caldera area affected by the eruption. This ratio quantifies how much of the caldera area with new volcano deposits is covered by our data. See Table \u003cspan refid=\"MOESM4\" class=\"InternalRef\"\u003eS4\u003c/span\u003e for exact values of A and A_er. V DRE is the total erupted volume in DRE, while M is the total erupted mass (see\u003c/em\u003e Section \u003cspan refid=\"Sec12\" class=\"InternalRef\"\u003e5\u003c/span\u003e \u003cem\u003efor details). For bistatic data acquired before November 2014, values in square brackets represent the lower and upper bounds of the bulk volume and of the mass.\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eV (x10\u003csup\u003e6\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eM (x10\u003csup\u003e9\u003c/sup\u003e kg)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePre-November 2014 data\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSRTM\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Feb. 2011 (desc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.40 [0.54 3.05]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.40 [0.54 3.05]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e26 Jun. 2011 (desc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.56 [0.79 2.73]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.56 [0.79 2.73]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e23 Feb. 2012 (desc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.97 [1.20 3.17]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.97 [1.20 3.17]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7 Jan. 2013 (desc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.88 [1.10 3.03]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.88 [1.10 3.03]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e23 Sep. 2013 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.12 [1.24 3.14]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.12 [1.24 3.14]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e27 Feb. 2014 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.34 [0.77 2.07]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.34 [0.77 2.07]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2014 EarthDEM\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Feb. 2011 (desc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e26 Jun. 2011 (desc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e23 Feb. 2012 (desc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.24\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7 Jan. 2013 (desc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e27 Feb. 2014 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.43 [0.56 7.91]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.43 [0.56 7.91]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eV (x10\u003c/b\u003e\u003csup\u003e\u003cb\u003e6\u003c/b\u003e\u003c/sup\u003e \u003cb\u003em\u003c/b\u003e\u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e% A/A_er\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eV DRE (x10\u003c/b\u003e\u003csup\u003e\u003cb\u003e6\u003c/b\u003e\u003c/sup\u003e \u003cb\u003em\u003c/b\u003e\u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eM (x10\u003c/b\u003e\u003csup\u003e\u003cb\u003e10\u003c/b\u003e\u003c/sup\u003e \u003cb\u003ekg)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2014\u0026ndash;2015 eruption\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSRTM\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Jan. 2019 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(25.45\u0026thinsp;\u0026plusmn;\u0026thinsp;1.04)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e80.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(18.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.60)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(5.02\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10 Dec. 2019 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(25.61\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e80.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(18.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.76)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(5.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCopernicus\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Jan. 2019 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(43.91\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(32.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(8.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10 Dec. 2019 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(47.30\u0026thinsp;\u0026plusmn;\u0026thinsp;1.80)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e78.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(34.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(9.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.33)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2014 EarthDEM\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Jan. 2019 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(42\u0026thinsp;\u0026plusmn;\u0026thinsp;3.12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(30.23\u0026thinsp;\u0026plusmn;\u0026thinsp;2.20)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(8.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.60)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10 Dec. 2019 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(43.90\u0026thinsp;\u0026plusmn;\u0026thinsp;3.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e72.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(31.48\u0026thinsp;\u0026plusmn;\u0026thinsp;2.52)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(8.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.69)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2018 EarthDEM \u0026minus;\u0026thinsp;2014 EarthDEM\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2018\u0026thinsp;\u0026minus;\u0026thinsp;2014 (EarthDEMs)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(61.24\u0026thinsp;\u0026plusmn;\u0026thinsp;8.38)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(42.62\u0026thinsp;\u0026plusmn;\u0026thinsp;5.75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(11.72\u0026thinsp;\u0026plusmn;\u0026thinsp;1.58)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e \u003cb\u003e2021 eruption (only pixels in the area covered by volcanic deposits associated to the 2021 eruption reported in Figure S19)\u003c/b\u003e \u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSRTM\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Jan. 2019\u0026ndash;15 Jul. 2021 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(5.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.78)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e72.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(3.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(0.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10 Dec. 2019\u0026ndash;15 Jul. 2021 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(4.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.72)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(3.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(0.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCopernicus\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3 Jan. 2019\u0026ndash;15 Jul. 2021 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(9.69\u0026thinsp;\u0026plusmn;\u0026thinsp;1.17)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(7.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.78)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(1.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10 Dec. 2019\u0026ndash;15 Jul. 2021 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(8.44\u0026thinsp;\u0026plusmn;\u0026thinsp;1.17)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(6.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.78)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(1.70\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2018 EarthDEM\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15 Jul. 2021 (asc.)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(11.96\u0026thinsp;\u0026plusmn;\u0026thinsp;3.95)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(8.34\u0026thinsp;\u0026plusmn;\u0026thinsp;2.78)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(2.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.76)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"6- Discussion","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e6.1 Height changes and the impact of the reference DEM used.\u003c/h2\u003e \u003cp\u003eBistatic pairs acquired before the November 2014 eruption show no significant topographic changes, with agreement among all the reference DEMs (Figures \u003cspan refid=\"MOESM5\" class=\"InternalRef\"\u003eS5\u003c/span\u003e-6). One exception is that all data compared to the SRTM DEM have a negative height change (NW-SE oriented) in the western sector of the caldera (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea-d,i-j), but there are no field data that allow us to understand if it might be a true anomaly, possibly due to a landslide occurred before 2011 (date of the first bistatic pair; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), or if it is only a result of an error in the SRTM DEM. Some small positive height changes recorded immediately to the E of this negative height change might support the landslide theory, representing the accumulation area of the deposits. Positive and negative height changes, with respect to all the reference DEMs used, recorded along the steep flank of the intra-caldera cone seem more related to a different estimate of the steepness of the cone recorded by the bistatic data with respect to that of the reference DEMs than to true height changes, as shown by elevation profiles (Figures \u003cspan refid=\"MOESM5\" class=\"InternalRef\"\u003eS5\u003c/span\u003e-6). However, we cannot exclude that some height changes in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e are related to the small explosive eruptions that occurred between the time of acquisition of the reference DEMs and the bistatic data, especially for the data processed with the SRTM (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). If all positive height changes of data processed with the SRTM were related to eruptive products, and not to errors in the DEM, the total erupted bulk volume would be of 0.54\u0026ndash;3.17 x10\u003csup\u003e6\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), equal to a magnitude 1.79\u0026ndash;2.5, which is also consistent with the VEI 1\u0026ndash;2 assigned by the GVP to explosive eruptions that occurred between the acquisition of the SRTM and of the bistatic data.\u003c/p\u003e \u003cp\u003eDescending orbit data acquired from June 2011 to 2013 and ascending orbit data acquired in 2014 show a low signal-to-noise ratio in the caldera area when processed with the 2014 EarthDEM (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef-h,k and Figures \u003cspan refid=\"MOESM5\" class=\"InternalRef\"\u003eS5\u003c/span\u003ed-f, S6d-f), suggesting that these bistatic pairs are noisier in the caldera area than the others. This also affects the volume change estimation, with the volume change estimated for the February 2014 bistatic data that is different than zero (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), although no eruption occurred between the acquisition of this data and that of the 2014 EarthDEM (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This hints that errors in the caldera could be sometimes larger than the error estimated in the reference areas outside the caldera. Similarly, also volumes estimated by the noisy data acquired from June 2011 to 2013 and processed with the 2014 EarthDEM (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) might be overestimated due to the low signal-to-noise ratio of these data. It is interesting to note that the same noisy ascending and descending data are less noisy when processed with the SRTM DEM, possibly due to the larger pixels size (30 m instead of the 3 m resolution of the bistatic data) that is each pixel value is an average of 100 pixels of the bistatic data, with positive and negative noisy pixels likely cancelling each other during the averaging. The lack of coherence in the SW area of the caldera in the bistatic pair acquired on 7 January 2013 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eh), processed with the 2014 EarthDEM, is possibly also related to the eruption that ended the day before the acquisition of this data.\u003c/p\u003e \u003cp\u003eBistatic pairs data acquired in 2019 allowed us to constrain the height changes associated with the November 2014-August 2015 eruption. Data processed with the SRTM DEM show lower (up to the 40\u0026ndash;50% in the caldera floor and up to the 45\u0026ndash;68% in the cone) height changes than those obtained from the same data processed with the other reference DEMs and with respect to those obtained by differencing the 2014 and the 2018 EarthDEMs (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Thus, the erupted volumes estimated from the bistatic data processed with the SRTM DEM are of ~\u0026thinsp;40\u0026ndash;59% lower than that estimated from the same data processed with the other reference DEMs (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Therefore, in this case the use of the SRTM DEM as the reference DEM leads to an erroneous calculation of the height changes and of the erupted volumes. This is possibly due to the high roughness of the SRTM topography in the S and W sector of the caldera floor (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), which are also the sectors where height changes were most underestimated within the caldera floor (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). On the contrary, bistatic pairs data processed with the Copernicus and the 2014 EarthDEM show height changes within the caldera floor that are consistent both with each other and with those calculated from differentiating the 2018 and the 2014 EarthDEMs. In addition, height changes in the caldera floor from these DEMs are also consistent with those inferred by Kaneko et al. (2019) using different sets of high-resolution satellite images. In the area of the intra-caldera cone we observe an overall lack of information, especially in data processed with the Copernicus DEM (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The loss of coherence can be related to both the high gradient of height change in the cone and to factors causing geometric decorrelation in steep areas, like shadows and layover effects (Kubanek et al., 2015b). Coherent pixels of bistatic data processed with the Copernicus and the 2014 EarthDEM DEMs in the intra-caldera cone show a small shift in the position of both the flanks and the summit of the intra-caldera cone with respect to the geometry recorded by the 2018 EarthDEM (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eg,h). This shift could be related to small errors in the geocoding of the bistatic data, or to small errors in the position of the cone in the 2018 EarthDEM. Bistatic data processed with the 2014 EarthDEM show higher height changes (up to 138 meters) at the top and in the SW flank of the intra-caldera cone with respect to those retrieved from differentiating the 2018 and the 2014 EarthDEMs (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). This implies that the 2019 bistatic pairs record a higher height of the cone formed during the 2014\u0026ndash;2015 eruption than the 2018 EarthDEM. The height recorded by the bistatic data is consistent with the maximum height of the cone (~\u0026thinsp;143 m) inferred by Kaneko et al. (2019).\u003c/p\u003e \u003cp\u003eThe bistatic pair data acquired in July 2021 provide us the opportunity to infer the height change and the associated erupted volume after the November 2014 - August 2015 eruption. Two eruptions occurred after the 2015 and before the date of acquisition of the July 2021 bistatic data (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e): a small explosive eruption in 2020 and a larger explosive to effusive eruption in January-April 2021. Since the height changes recorded by our data match well with the location of the 2021 lava flows and the associated new intra-caldera cone (Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef-h, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg-i, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e), here we assume that all the height changes recorded by the 2021 bistatic data are related to the January-April 2021 eruption.\u003c/p\u003e \u003cp\u003eAs with the 2014\u0026ndash;2015 eruptions, height changes in the caldera floor area from the 2021 eruptions obtained from the difference of the bistatic data processed with the SRTM DEM are ~\u0026thinsp;44\u0026ndash;64% lower than those estimated from data processed with the Copernicus DEM and with the 2018 EarthDEM (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e and Figure S19). The bistatic pairs data processed with the 2018 EarthDEM shows also much higher height changes (up to 124m) in the intra-caldera cone with respect to the data processed with SRTM DEM, while data processed with the Copernicus DEM are incoherent in this area.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e6.2 Magnitude of the eruptions\u003c/h2\u003e \u003cp\u003eWe estimated from differencing the 2018 and the 2014 EarthDEMs a bulk volume of 61.24\u0026thinsp;\u0026plusmn;\u0026thinsp;8.38 x10\u003csup\u003e6\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e of magma erupted during the November 2014 \u0026ndash; August 2015 eruption, which corresponds to a DRE volume of 42.62\u0026thinsp;\u0026plusmn;\u0026thinsp;5.75 x10\u003csup\u003e6\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e and to a mass of 11.72\u0026thinsp;\u0026plusmn;\u0026thinsp;1.58 x10\u003csup\u003e10\u003c/sup\u003e kg of magma (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), equal to a Magnitude 4.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 eruption. Volumes and masses estimated from bistatic pairs data acquired in 2019 and processed with the Copernicus and the 2014 EarthDEM are ~\u0026thinsp;19\u0026ndash;31% lower (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), but this discrepancy is explained by the fact that these data do not maintain coherence in ~\u0026thinsp;20\u0026ndash;30% of the caldera area covered by volcanic products of this eruption, especially in the cone area (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and Table \u003cspan refid=\"MOESM4\" class=\"InternalRef\"\u003eS4\u003c/span\u003e). Kaneko et al. (2019) estimated a volume of 74.8\u0026thinsp;\u0026plusmn;\u0026thinsp;11.2 x10\u003csup\u003e6\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e for this eruption, but they converted the volume of the cone in DRE assuming a lava density of 2500 kg/m\u003csup\u003e3\u003c/sup\u003e and pyroclastic material density of 1000 kg/m\u003csup\u003e3\u003c/sup\u003e and they did not correct the volume of lavas emplaced in the caldera floor for vesicularity. With the same assumptions, we would obtain a volume of 56.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.54 x10\u003csup\u003e6\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e, still quite consistent with that from Kaneko et al. (2019), although the volume of the intra-caldera cone estimated by these authors do not come directly from data as in our case, but was assumed to be equivalent to that of a conical solid having a height of 143 m and a basal planar radius of 279 m at which they subtracted the volume of the pre-eruptive cone assumed equal to a cone having a height of 35 m and a basal planar radius of 279 m.\u003c/p\u003e \u003cp\u003eAs for the January-April 2021 eruption, volumes and masses estimated from data processed with the SRTM are ~\u0026thinsp;41\u0026ndash;64% lower than that estimated from data processed with the 2018 EarthDEM and with the Copernicus DEM (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The Magnitude associated to data processed with the Copernicus DEM and with the 2018 EarthDEM ranges from 3.2 to 3.5. However, also in this case, data do not maintain coherence in ~\u0026thinsp;30% of the caldera area covered by volcanic products of this eruption (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), especially in the zone of the intra-caldera cone. Data processed with the 2018 EarthDEM shows a maximum height change in the cone of ~\u0026thinsp;124 meters and therefore the lack of data in ~\u0026thinsp;64\u0026ndash;85% of the cone (Table \u003cspan refid=\"MOESM4\" class=\"InternalRef\"\u003eS4\u003c/span\u003e) can generate an important underestimation of the total volume, also considering that lavas in the caldera floor have a lower height and cover a lower surface than lavas of the 2014\u0026ndash;2015 eruption and, therefore, have less impact on the total volume of the 2021 eruption.\u003c/p\u003e \u003cp\u003eTo have an idea of the amount of the volume underestimated due to the lack of coherence, we used two different approaches. First, we interpolated the 2021 bistatic data processed with the 2018 EarthDEM, which is the only DEM that maintains some coherence in the intra-caldera cone (Figure S20 and Table \u003cspan refid=\"MOESM6\" class=\"InternalRef\"\u003eS6\u003c/span\u003e). We are aware that the interpolation in the cone area is not correct from a theoretical point of view, due to the lack of data in the east and central portion of the cone (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ee) that potentially leads to large interpolation errors in this area, but at least it provides a raw value of the potential volume lost by incoherent pixels. Second, we assume a conical geometry of the intra-caldera cone, with a radius of 280 meters and a maximum height of 124 meters (from the bistatic data processed with the 2018 EarthDEM), and we calculated the associated volume (Table \u003cspan refid=\"MOESM6\" class=\"InternalRef\"\u003eS6\u003c/span\u003e). Although these estimations should not be considered exact values of the volume of the cone, they hint that the bulk volume of the cone might be 73\u0026ndash;98% higher than that estimated from our analysis. The magnitude of the eruption would pass from 3.36 (estimated from the 2021 bistatic data processed with the 2018 EarthDEM; Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) to 3.44\u0026ndash;3.50 (Table \u003cspan refid=\"MOESM6\" class=\"InternalRef\"\u003eS6\u003c/span\u003e) and from 3.23\u0026ndash;3.29 to 3.35\u0026ndash;3.46 by extrapolating values of the cone in Table \u003cspan refid=\"MOESM6\" class=\"InternalRef\"\u003eS6\u003c/span\u003e to the data processed with the Copernicus DEM.\u003c/p\u003e \u003cp\u003eAs expected for effusive eruptions, the Magnitude we estimated for the November 2015 \u0026ndash; August 2015 and for the January-July 2021 (4.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 and 3.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14 respectively) is higher than the VEI 2 assigned by the Smithsonian Global Volcanism Program to these eruptions, with important implication in the recent eruptive rates of this volcano. Furthermore, it is important to note that volumes and masses estimated in our analysis refer only to volcanic products deposited within the caldera of Raung, while an unknown mass of ash associated to the volcanic plumes of these eruptions (e.g. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee) has been carried away by winds and deposited outside the caldera.\u003c/p\u003e \u003c/div\u003e"},{"header":"7- Conclusions","content":"\u003cp\u003eWe used high-resolution DEMs derived from SAR bistatic data and optical EarthDEMs to investigate the eruptive activity at Raung volcano. We found that the reference DEM used to process bistatic data can significantly affect the estimation of height changes and volumes, especially if the DEM is characterized by a noisy rough pre-eruptive topography, as the case of the SRTM DEM. On the contrary, despite their different spatial resolutions (30m vs. 3m), data processed with the Copernicus DEM are consistent with that processed at full resolution with the EarthDEMs, although these latter data maintain better coherence in steep areas, such as those of the intra-caldera cone. However, areas with steep slopes, like that of the cone, in all the bistatic data experience at least a partial loss of coherence and information, regardless the reference DEM used. This is likely also due to factors causing geometric decorrelation of bistatic data in steep areas, like shadows and layover effects, limiting the applicability of DEM derived by these data to calculate the topographic changes over the entire steep slopes.\u003c/p\u003e \u003cp\u003eOur results show that DEMs acquired before the November 2014 eruption are characterized by small height changes where it is difficult to separate true signals from errors. Thus, volume change connected to Magnitude 2, or smaller, explosive eruptions, as those occurred before November 2014, are difficult to calculate from these data. On the other hand, these data can be used to map at high resolution the topographic changes due to Magnitude\u0026thinsp;\u0026ge;\u0026thinsp;3 eruption and to calculate the erupted volumes from them. With these data we determine a DRE volume of 42.62\u0026thinsp;\u0026plusmn;\u0026thinsp;5.75 x10\u003csup\u003e6\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e for volcanic products deposited within the caldera of Raung during the November 204 - August 2015 eruption, quite consistent with that estimated by Kaneko et al. (2019) (see section \u003cspan refid=\"Sec15\" class=\"InternalRef\"\u003e6.2\u003c/span\u003e). A minimum DRE volume of 8.34\u0026thinsp;\u0026plusmn;\u0026thinsp;2.78 x10\u003csup\u003e6\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e has been estimated for volcanic deposits within the caldera of Raung associated to the January-April 2021 eruption, but our data do not maintain coherence in the whole area of the caldera covered by deposits of this eruption (especially in the cone), potentially missing a 16\u0026ndash;27% of the DRE erupted volume. Our analysis reveals that after many years (at least from 2000 to October 2014; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) characterized by mild explosive volcanic activity, with only tephra emission, Raung experienced a Magnitude\u0026thinsp;\u0026ge;\u0026thinsp;4 and a Magnitude\u0026thinsp;\u0026gt;\u0026thinsp;3.0 eruption in seven years, with the production of lavas. Time series of high resolution DEMs derived from satellite data provide therefore a powerful tool to quantify masses erupted by Magnitude\u0026thinsp;\u0026ge;\u0026thinsp;3 eruptions, which can be used in future studies to develop physics-based models coupling extrusion rates with other monitoring parameters, like deformation and thermal data, to further improve the knowledge of the magmatic systems and the volcanic activity at Raung and to try forecasting its future eruptive rates (Anderson and Segall 2011; Coppola et al. 2023).\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003e \u003cb\u003eCompeting interests\u003c/b\u003e:\u003c/strong\u003e \u003cp\u003ewe declare to do not have financial interests that are directly or indirectly related to this work.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eF. Galetto and M. E. Pritchard were supported by 80NSSC21K0842 issued through NASA\u0026rsquo;s Science Mission Directorate\u0026rsquo;s Earth Science Division, which also provided the access to the bistatic TSX/TDX data.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eCopernicus DEM (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5270/ESA-c5d3d65\u003c/span\u003e\u003cspan address=\"10.5270/ESA-c5d3d65\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e) is open source and is freely available at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://portal.opentopography.org/raster?opentopoID=OTSDEM.032021.4326.3\u003c/span\u003e\u003cspan address=\"https://portal.opentopography.org/raster?opentopoID=OTSDEM.032021.4326.3\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. The NASA SRTM DEM is open source and is freely available at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://earthexplorer.usgs.gov/\u003c/span\u003e\u003cspan address=\"https://earthexplorer.usgs.gov/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e or at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://portal.opentopography.org/raster?opentopoID=OTSRTM.082016.4326.1\u003c/span\u003e\u003cspan address=\"https://portal.opentopography.org/raster?opentopoID=OTSRTM.082016.4326.1\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. Strip EarthDEM (Porter et al. 2022) is available to U.S. federal employees/contractors and federally-funded researchers. Maxar data in Fig.\u0026nbsp;3 comes from GoogleEarth pro, while Sentinel data are freely available are freely provided through the Copernicus Program of the European Union (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://dataspace.copernicus.eu/browser/\u003c/span\u003e\u003cspan address=\"https://dataspace.copernicus.eu/browser/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). The Umbra data used in Fig.\u0026nbsp;4 are freely provided by the vendor at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://umbra-open-data-catalog.s3-website.us-west-2.amazonaws.com/?prefix=sar-data/tasks/Volcanoes/\u003c/span\u003e\u003cspan address=\"http://umbra-open-data-catalog.s3-website.us-west-2.amazonaws.com/?prefix=sar-data/tasks/Volcanoes/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAnderson K, Segall P (2011) Physics-based models of ground deformation and extrusion rate at effusively erupting volcanoes. 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Netherlands Journal of Sea Research 24:303\u0026ndash;312. https://doi.org/10.1016/0077-7579(89)90156-7\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZink M, Moreira A, Hajnsek I, et al (2021) TanDEM-X: 10 Years of Formation Flying Bistatic SAR Interferometry. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 14:3546\u0026ndash;3565. https://doi.org/10.1109/JSTARS.2021.3062286\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bulletin-of-volcanology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"buvo","sideBox":"Learn more about [Bulletin of Volcanology](http://link.springer.com/journal/445)","snPcode":"445","submissionUrl":"https://www.editorialmanager.com/buvo/default2.aspx","title":"Bulletin of Volcanology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Raung volcano, volcano topography change, remote sensing volcano geodesy, erupted masses","lastPublishedDoi":"10.21203/rs.3.rs-4364766/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4364766/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eQuantifying erupted masses of magma is fundamental to determine the size of eruptions. Pre- and post- eruptive Digital Elevation Models (DEMs) derived from satellite data can quantify erupted masses, even in remote areas. Here we used bistatic Synthetic Aperture Radar (SAR) data from the TanDEM-X satellite and EarthDEMs derived by stereo-optical data, to investigate topographic changes and the erupted mass at the caldera of Raung (Indonesia), which is one of the most frequently erupting volcanoes on Java. We found that erupted masses associated with Magnitude\u0026thinsp;\u0026le;\u0026thinsp;2 eruptions occurred from 2000 to mid-2014 are difficult to be estimated with these DEMs, due to the difficultly to separate the signal of the limited amount of ash deposited within the caldera from data errors. On the contrary, these DEMs mapped at high resolution deposits of Magnitude\u0026thinsp;\u0026ge;\u0026thinsp;3 eruptions. The November 2014 \u0026ndash; August 2015 eruption produced 11.72\u0026thinsp;\u0026plusmn;\u0026thinsp;1.58 x10\u003csup\u003e10\u003c/sup\u003e kg of magma (Magnitude 4.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06), generating lava flows with a maximum height of ~\u0026thinsp;46\u0026ndash;50 meters and a new intra-caldera cone. The January-April 2021 eruption, never studied before, erupted at least 2.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.76 x10\u003csup\u003e10\u003c/sup\u003e kg of magma (Magnitude 3.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15), generating lava flows (maximum thickness\u0026thinsp;~\u0026thinsp;16\u0026ndash;21 meters) and the growth of the intra-caldera cone. Our analysis reveals that the different pre-eruptive DEMs used to process SAR data and calculate topographic and volume changes can affect extrusive mass estimates by up to ~\u0026thinsp;60%. Erupted masses at Raung here estimated could be used in future studies to develop physics-based models coupling extrusion rates with other monitoring parameters to further improve the knowledge of this frequently erupting volcano.\u003c/p\u003e","manuscriptTitle":"The use of high-resolution satellite topographic data to quantify volcanic activity at Raung volcano (Indonesia) from 2011 to 2021","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-14 15:57:30","doi":"10.21203/rs.3.rs-4364766/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Moderate revision (possibly re-reviewed)","date":"2024-09-10T18:10:07+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-06-03T17:34:45+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-02T15:24:18+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Bulletin of Volcanology","date":"2024-05-20T11:44:32+00:00","index":"","fulltext":""},{"type":"submitted","content":"Bulletin of Volcanology","date":"2024-05-06T11:04:42+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bulletin-of-volcanology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"buvo","sideBox":"Learn more about [Bulletin of Volcanology](http://link.springer.com/journal/445)","snPcode":"445","submissionUrl":"https://www.editorialmanager.com/buvo/default2.aspx","title":"Bulletin of Volcanology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"439f115f-3431-410c-8a74-2365920970e9","owner":[],"postedDate":"June 14th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-12-09T16:10:31+00:00","versionOfRecord":{"articleIdentity":"rs-4364766","link":"https://doi.org/10.1007/s00445-024-01781-1","journal":{"identity":"bulletin-of-volcanology","isVorOnly":false,"title":"Bulletin of Volcanology"},"publishedOn":"2024-12-02 15:57:39","publishedOnDateReadable":"December 2nd, 2024"},"versionCreatedAt":"2024-06-14 15:57:30","video":"","vorDoi":"10.1007/s00445-024-01781-1","vorDoiUrl":"https://doi.org/10.1007/s00445-024-01781-1","workflowStages":[]},"version":"v1","identity":"rs-4364766","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4364766","identity":"rs-4364766","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}