Magma migration beneath the active craters of Sakurajima volcano before the 2023 eruption of Showa crater inferred from ground deformation and muon monitoring

Magma migration beneath the active craters of Sakurajima volcano before the 2023 eruption of Showa crater inferred from ground deformation and muon monitoring | 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 Magma migration beneath the active craters of Sakurajima volcano before the 2023 eruption of Showa crater inferred from ground deformation and muon monitoring László Oláh, Haruhisa Nakamichi, Takao Ohminato, Hiroyuki K. M. Tanaka, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6573242/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Dec, 2025 Read the published version in Earth, Planets and Space → Version 1 posted 4 You are reading this latest preprint version Abstract Ground deformation source modeling and muographic mass density monitoring were applied for studying the plumbing system of Sakurajima volcano, Kyusu Japan using data collected by Interferometric Synthetic Aperture Radar and Sakurajima Muography Observatory. Lateral movement of ground deformation source was observed to east beneath the active craters around sea level that resulted in the shift of eruption frequency between the Minamidake craters. During the same period, muography showed opposite trends in mass changes for adjacent craters: mass decreased beneath the Minamidake A crater and Minamidake B craters and mass increased beneath the Showa crater that also suggests the lateral movements of materials towards east. Thereafter, the ground deformation source started to rise and the eruption sequence of Showa crater started when the deformation source reached a depth of about 350 m. The muographically measured mass increased beneath Showa crater before the start of the eruption sequence. During eruption episodes of Minamidake A and B craters the mass did not change beneath these craters and decreased beneath Showa crater that suggest a connection between the adjacent craters. These observations suggest the presence of a deep magma channel around sea level which feeds Minamidake A and Minamidake B craters and the existence of a shallow magma chamber about 350 m beneath the active craters which feeds all craters. Joint measurement of ground surface deformations and cosmic-ray muons allows simultaneous monitoring of deep and shallow volcanic processes that may allow more reliable assessment of impending eruption sequences of Showa crater of Sakurajima volcano. Muography cosmic-ray muon InSAR ground deformation volcano magma conduit Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Integration of complementary geophysical, geochemical and petrological observations may allow us to explore the magma plumbing system, to study the volcanic processes that generate magma movements and to elucidate how magma intrusion affects volcano deformation, eruption dynamics, etc. (Sparks et al. 2012 ; Magee et al. 2018 ). Monitoring the spatio-temporal evolution of magma has successfully been applied for determining the spread of volcanic edifice (Donnadieu et al. 2001a, 2001b ), localizing the onset of impending eruptions (D’Auria et al. 2012 ; Cannavó et al. 2015), revealing the open of new fissures (Pagli et al. 2012 ), and assessing the occurrence of flank failures (Cervelli et al. 2006 ; Bonforte et al. 2015) and possible secondary effects of these hazards, such as tsunamis (Cervelli et al. 2002 ) or pyroclastic density currents (Belousov et al. 2020) that can affect even distant areas and result in more devastation. Interferometric Synthetic Aperture Radar (InSAR) allows the detection of magma accumulation and tracking magma migration (Biggs et al. 2014 ). InSAR measures either pre-eruptive inflation of ground surface due to magma intrusion (Patané et al. 2003 ) or syn-eruptive deflation of the volcanic edifice due to release of volcanic ejecta (Massonnet et al. 1995 ). InSAR can be applied even at remote, inaccessible volcanic edifices. Modeling allows to create a linkage between subsurface deformation sources and the measured surface deformation: helps to interpret ground surface deformations and determine the position, volume and pressure changes of magmatic ground deformation sources (e.g., Mogi 1958 ; McTigue 1987 ; Lisowski 2007 ). Compiling global InSAR data sets and interpreting ground deformation and other monitoring data allowed to reveal some limitations of InSAR: (A) About half of volcano deformations followed by eruptive activities and less than one-tenth of volcanoes erupted without precursory ground surface deformations (Biggs et al. 2014 , Reath et al. 2019 ). (B) The ground surface deformations are indirect effects of subsurface phenomena, e.g., dormant craters can also uplift due to inflation source located beneath the adjacent crater on multi-vent volcanoes (Oláh et al. 2023 ). (C) Elastic models can not distinguish whether the effects on the intrusion are caused by pressure change or magma recharge (Fernández et al. 2001 ). (D) Modeling is sensitive to the presence of weak materials within the caldera (Masterlark 2007 ). Applying mass density sensitive complementary techniques, such as gravimetry (e.g., Fernández et al. 2001 ; Battaglia & Segall 2004; Poland et al. 2023) or muography (e.g., Tanaka et al. 2019, 2023 ; Gibert et al 2022 ; Macedonio et al. 2022 ), not only contributed to revealing the aforementioned limitations, but these may help to distinguish whether ground deformations are caused either pressure changes or mass movements (Fernández et al. 2001 ; Oláh et al. 2023 ). Muography is based on the measurement of the yield of cosmic-ray muon particles. Muons are naturally occurring elementary particles created at 10–15 km altitude in Earth’s atmosphere as the end product of particle physics processes induced by collisions of primary cosmic-rays with the atmospheric nuclei. Muography allows remote, passive and high-resolution scanning of the internal structure of large-sized structures, including volcanic edifices. The finite yield of muons (10,000 per square meter per minute at sea level) is reduced with 3–4 orders of magnitudes after penetrating rocks with a thickness of a few hundreds of meters, thus the applicability of muography is limited for the craters and upper conduits of volcanoes. Magmatic materials have already been imaged and monitored by muography. Tanaka et al. ( 2014 ) observed the uprise of magma in the conduit of Satsuma-Iwojima volcano during the 2013 eruption. Kusagaya & Tanaka ( 2015 ) revealed a dense region in Usu volcano that was interpreted as a past magma intrusion. Joint inversion of muographic and gravimetric data revealed an intruded magma body with cylindrical shape in Showa-Shinzan lava dome (Nishiyama et al. 2017 ). Multi-directional muography explored highly welded vent of the scoria cone and three-directional radial dikes extending from the central vent in Omuro-yama scoria cone (Nahagara et al. 2022). A magmatic body was visualized in the summit of Puy de Dôme volcano (Portal et al. 2013 ). We imaged plug formation (Oláh et al. 2019 ), explained a linkage between ground surface deformation and eruption frequency (Oláh et al. 2023 ) and explored the conduit structure (Oláh et al. 2024 ) in Sakurajima volcano, Japan. Sakurajima volcano is supplied with magma from the Aira caldera located in Kagoshima Bay and its southern peak is erupting from three craters, namely Minamidake A, Minamidake B and Showa. The type of eruptive activity is primarily Vulcanian (Gabellini et al. 2023). Eruption mechanism has been understood (Uhira et al. 1994; Iguchi 2011, 2013; Kazahaya et al. 2016 ). Different parts of the plumbing system have already been explored: Continuous magnetotelluric observations revealed electrical resistivity changes due to movement of mixture of magma and ground water around the sea level (Aizawa et al. 2011 ). Absolute gravity measurements reconstructed the possible altitude of the magma head between 400 m and 800 m altitudes above sea level (ASL) (Okubo et al. 2013 ). Vent radii of Showa was estimated to 30–50 m from infrasound data (Muramatsu et al. 2018 ). The hypocenters of the earthquakes associated with explosive eruptions are estimated to be at the depth of 500 m beneath the active craters by the seismic structure of the artificial seismic experiment (Nishimura et al. 2024 ). Muographically measured mass density changes allowed to infer to a branched connection between the Minamidake B and Showa craters (Oláh et al. 2024 ). In recent years, the eruptive frequency was observed typically a few tens of eruptions per month with a few dormant periods (Fig. 1 a-c). Minamidake A and Minamidake B erupted in recent years and the Showa activated from 8 February to 4 August 2023. In this work, we analyse ground surface deformation and muon monitoring data to track the possible precursory magma migration before the eruption sequence 2023 of Showa crater and infer the structure of the plumbing system. 2. Data collection and analysis methods 2.1 Experimental setting and data collection Ground surface deformation of the volcanic edifice and the yield of cosmic-ray muons across the region of active craters were measured to observe simultaneously and interpret together both deep and shallow signals of volcanic activities. Our experimental setting is presented in Fig. 1 d. Vertical displacements of the southern peak around the active craters were determined using the Phased Array type C-band Synthetic Aperture Radar images acquired by Sentinel-1 (The European Space Agency 2022) with a periodic time of 12 days (NEC 2025 ). NEC Corporation analyzed the InSAR images independently from this work and provided the vertical uplift data (Oláh et al. 2023 , 2024 ). The vertical displacements were determined relative to the ground level measured on 6 April 2021 at 150 locations for the period from April 2021 to April 2023. The yield of cosmic-ray muons was monitored across the southern peak of Sakurajima volcano with the Multi-Wire Proportional Chamber (MWPC)-based Muography Observation System (MMOS) of Sakurajima Muography Observatory (Oláh et al 2019 , 2023 , 2024 ). The MMOS is a modular system that is operated with ten tracking system modules at longitude of 31.557° and latitude of 130.650° at a distance of approx. 2,800 m from the active craters of Sakurajima volcano at 150 m ASL. The MMOS has already been presented extensively in Refs. (Oláh et al. 2018 , 2021 ; Varga et al. 2020 ). We conducted data collection continuously between 1st October 2020 and 31th March 2023. Collection of muographic data has been stopped once per year when maintenance of MMOS was conducted. 2.2 Mogi modeling of ground surface deformations Ground surface deformations were localized near the peak region around the active craters which hinted that the source of deformations may be located near the surface of the volcanic edifice. We localized the deformation source via quantifying the volume change ( ΔV ), depth ( D ), longitude and latitude coordinates by Mogi modeling of vertical displacements ( U v ) (Mogi 1958 ; McTigue 1987 ; Lisowski 2007 ). Figure 2 a visualizes a magma body as a small spherical pressure source of ground surface deformations. The magma body has an r radius that is significantly smaller than its D depth. The surface displacement occurs in radial directions due to pressure change in the small spherical volume. The vertical component of ground surface deformation ( U v ) at an R radial distance from the the deformation source is expressed by the following equation: U v = 3 ΔV D / [ 4π ( R 2 + D 2 ) 3/2 ] . (1) Parameter estimation procedure based on grid searching via minimizing the relative difference between the measured and modeled vertical uplifts ( U v ) of ground surface as a function of the lateral distance of measurement point from the deformation source ( R ). Four model parameters were varied: the ΔV volume change, the longitude coordinate, latitude coordinate and D depth from the level of the crater floor. The measured vertical uplift data were considered for altitudes above 700 m ASL for this analysis. The ΔV volume change was varied from 30 Mm 3 to 50 Mm 3 with a step size of 5 Mm 3 . The longitude and latitude coordinate was respectively set to different values in a range from 130.658° to 130.660° and from 31.579° to 31.581°. The step size was set 0.00025° and 0.00050° for the longitude and the latitude, respectively. The D depth from the crater floor was varied from 100 m to 1000 m with a step size of 25 m. Figure 2 b shows an example for comparison of vertical uplifts versus radial distance from source location for experimental (yellow-coloured dot) data set and for the Mogi modelling (black solid line). 2.3 Muon data analysis and modeling Event-by-event analysis procedure has been presented extensively in Ref. (Oláh et al. 2024 ). Here we describe the analysis procedure in a nutshell. The procedure is initiated with reconstruction of clusters of muon hits on chamber by chamber. This reconstruction determined the cluster’s centroids, sizes and numbers. Thereafter, a combinatorial algorithm gathered the cluster centroids into track candidates and ordered them based on the goodness of line fit (chi-square per number of degrees of freedom, χ 2 /ndf , where the ndf equals to number of detectors minus two), and selected the best fitting track candidate with the smallest χ 2 /ndf . In the last step, a track count histogram with a bin size of 0.023 in both directions was filled based on the horizontal and vertical slopes of tracks. After filling the track count histogram, flux was calculated for each angular bin by dividing the track counts with sensitive surface area, solid angle and effective measurement time. Statistical flux error was determined by dividing the square root of track counts with the same quantities. Forward modelling of flux was conducted to determine the density across the volcanic edifice. The modeled flux was determined with different density-lengths (density integrated over path-length) by integrating the energy and elevation angle dependent spectra of muons (Tang et al. 2006 ) from threshold energies that are required for muons to penetrate the given density-lengths (Groom et al. 2002 ). Path-lengths were calculated using the digital elevation model of the edifice (Geospatial Authority of Japan 2024). The density value was extracted when the difference between the measured and modeled muon fluxes was found to be minimal. Figure 3 shows the densities for the measurement period with a bin size of 0.023 in both horizontal and vertical direction. This bin size corresponds to a spatial resolution of about 60 m from the distance of 2,800 m. The mass ( m ) was calculated for each region by summing up the masses that were quantified as follows. m = ∑ i ρ i ✕ T i ✕ D 2 ✕ Δtan(θ x ) ✕ Δtan(θ y ), (2) where ∑ runs over the pixels within the selected region, ρ i is the density in pixel i, T i is the thickness along pixel i, D is the distance of 2,800 m between the SMO and volcanic edifice, Δtan(θ x ) and Δtan(θ y ) are respectively the horizontal and vertical pixel sizes. 3. Results 3.1 Tracking deep magma migration by modeling ground deformation source Figure 4 shows respectively the variations of the modeled parameters (black circles connected with solid lines) of Mogi source from April 2021 to April 2023 and the eruption frequencies of active craters (coloured boxes) from January 2021 to December 2023. The volume change of the Mogi source was found to be about 30,000–40,000 m 3 during the entire period (Fig. 4 a). The source kept its latitude within a range of 31.579°-31.581°, i.e., it moved neither to north nor to south throughout the measurement period from beneath the active craters (Fig. 4 b). The variations of longitude coordinate indicate that the source of ground deformation shifted from the region located beneath Minamidake A crater to a region located beneath Minamidake B and Showa crater from April 2021 (Fig. 4 c). This horizontal movement may resulted in the shift of eruptive activity from Minamidake A (blue boxes) to Minamidake B (green boxes). Throughout the entire measurement period, the Mogi source uplifted from 700 m depth (sea level) to 330 m depth (370 m ASL) relative to the level of Showa crater’s floor (700 m ASL) (Fig. 4 d). Since the latitude of the Mogi source remained within a narrow range, we combined the longitudinal and the vertical variations of the Mogi source in Fig. 4 e. Here the horizontal coordinates are shown relative to the observation axis (black arrow of Fig. 1 d) of the muography observation instrument. The depth is measured relatively to the floor of Showa crater. The shape of crater floors (black solid line) were extracted along the PQ line of Fig. 1 d. Two phases are indicated for the movement of the Mogi source: (1) a rapid horizontal shift between the Minamidake A and Minamidake B occurred in 2021 and (2) a slower uplifting. The eruption sequence of Showa crater started when the source reached the depth of about 350 m (350 m ASL) in February 2023 (yellow boxes in Fig. 4 c). 3.2 Muon monitoring of shallow material transfers We conducted off-line analysis of muographic data (Oláh et al. 2024 ). The analysis procedures are presented in a nutshell in section Methods. In this work, we reconstructed the mass density images across the crater region and determined the total mass beneath the active craters. Figure 5 a- 5 c show the 6 month average (arithmetic mean values) of masses with one standard deviation (black dots with error bars) for the regions beneath Minamidake A, Minamidake B, and Showa craters (black rectangles in Fig. 4 e) and the monthly number of eruptions (colored boxes) from January 2021 to January 2024. Simultaneous changes were observed in the masses from January 2021 to March 2022: the total mass decreased beneath Minamidake A and Minamidake B with about 10–15 Mt and increased beneath Showa with about 8 Mt. Throughout the same period, the eruptive activity shifted from Minamidake A (blue boxes) to Minamidake B (green boxes). The masses did not change beneath the craters during a relatively dormant period from March 2022 to May 2022. The masses increased beneath Minamidake A, Minamidake B and decreased beneath Showa crater during the eruptive activities of the former two craters from May 2022 to October 2022. From November 2022 to May 2023, the mass started to decrease beneath Minamidake A and Minamidake B until the end of their eruption episodes and the mass increased beneath Showa crater. Between May 2023 and August 2023, the mass decreased beneath Showa crater until the end of the eruption sequence. During the same period, the masses increased beneath the dormant Minamidake A and Minamidake B craters. After the end of the eruption sequence in August 2023, the mass did not change beneath the Showa crater. Besides the crater regions the average mass was monitored across a reference region in which volcanism did not occur and the mass did not change here during the entire data collection period (Oláh et al. 2024 ). 4. Discussion and conclusions Joint observation of Sakurajima volcano has been conducted with ground deformation and muon monitoring. Ground deformation source was modeled for tracking the deep processes. Muography was conducted for monitoring the mass changes across the shallow regions of volcanic edifice. The finite yield of muons allowed the imaging of the upper 120 m parts of conduits and craters of Sakurajima volcano during the measurement periods of 6 months. The mass sensitivity of muography allowed (1) to localize the ground deformation source of the uplift more in a pin-point way than InSAR, e.g., in a previous work the ground deformation data showed uplift in the region of Showa Crater but it was caused by the magma located beneath Minamidake Crater (Oláh et al 2023 ), and (2) helped to distinguish between the pressure change induced or mass intrusion induced ground deformations. Although muography could not pin-point the source of ground deformation in these regions, the mass changes due to compressions and decompressions in mixture of gaseous and liquid materials beneath the volcanic plug could be quantified and shallow volcanic processes could be studied more accurately. The observational results are discussed together for the following periods as follows. From January 2021 to March 2022 a lateral movement of ground deformation source occurred at a depth of 600–700 m beneath the floor of Showa crater. During the same period, the mass changes were respectively observed beneath the two Minamidake craters and the Showa crater to -10-15 Mt and + 8 Mt that also indicates material transfer towards Showa crater. Our interpretation is that the observed material transfers resulted in the shift of eruptive activities from Minamidake A (blue boxes in Fig. 4 c) to Minamidake B (green boxes in Fig. 4 c). The depth of lateral movement of the ground deformation source was found to be consistent with the depth of a fracture network reconstructed with magnetotelluric (MT) measurements conducted at 3.3 km east and 3 km west from Minamidake crater in 2008–2009 (Aizawa et al. 2011 ). The resistivity increased around sea level beneath the eastern measurement site in coincidence with the volcanic unrest. This resistivity increase was interpreted as a sign of lateral degassing of volatiles from a magma body. The results suggested the presence of a fracture network at a depth around sea level in which a mixture of ground water and degassed volatiles can migrate laterally. Results of ground deformation source modeling also support the presence of this lateral fracture network. During the eruption sequences of Minamidake B and Minamidake A craters occurred from May 2022 to October 2022, the masses increased with about 15 Mt beneath Minamidake A, Minamidake B and decreased with about 10 Mt beneath Showa crater. These trends suggest material transfer from a shallow region beneath Showa crater to a shallow region beneath Minamidake craters. Magma intrusion may caused the remaining mass increase. During the period from November 2022 to May 2023, mass started to decrease beneath Minamidake A and Minamidake B until the end of their eruption episodes and densities increased beneath Showa crater. Eruptive activities started in the Showa crater in February 2023 when the ground deformation source rose to the depth of about 350 m beneath the bottom of Showa crater (350 m ASL). These observations suggest that the Showa crater activates when the magma reaches a sufficiently shallow depth beneath the active craters. This is similar to what was observed before earlier eruption episodes of Showa crater when the magma head was quantified between 400 m and 800 m ASL by the absolute gravity measurements (Okubo et al. 2013 ). It is worth to note that the difference between the altitude of current floor level and earlier reconstructed source altitude originates from deepening and widening of Showa crater (Japan Meteorological Agency 2018 ). Between May 2023 and August 2023, the mass decreased with 10 Mt beneath Showa crater until the end of the eruption sequence. We interpret this mass decrease as decrease in magma feeding and release of volcanic ejecta. Former one resulted in the stop of eruptive activity. This is consistent with our earlier observations for the active Mindamidake craters (Oláh et al. 2023 , 2024 ). Observing a mass transfer between the active craters at shallow depth and activation of Showa crater as ground deformation source reach shallow depths of below 350 m support the presence of a common shallow magma storage and conduit system beneath the three craters. Seismic sources of explosive eruptions are located in and around a region at a depth of 400 m (Nishimura et al. 2024 ). Furthermore, geochemical analysis of samples from ejected rocks indicated that these rock samples are identical and originate from the same source (Matsumoto et al. 2023). Similar structure was observed at Mt. Etna in which short-term magma storage occurred close to the surface before a flank eruption and summit eruptive activity from a source located at larger depth (Sanderson 1982 ). Joint analysis of ground deformation and muon data improves reliability of the monitoring of shallow parts of volcano’s plumbing system and may allow more robust assessment of impending eruption sequences of Showa crater. Abbrevations ASL Above Sea Level InSAR Interferometric Synthetic Aperture Radar MMOS MWPC-based Muography Observation System MT Magnetotelluric MWPC Multi-Wire Proportional Chamber ndf Number of Degrees of Freedom Declarations Availability of data and materials The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests Not applicable. Funding This work was supported by the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Integrated Program for the Next Generation Volcano Research, the Joint Usage Research Project (JURP) of the University of Tokyo, Earthquake Research Institute, University of Tokyo (ERI) under project ID 2023-H-03, the Hungarian NKFIH research grant under identification number TKP2021-NKTA-10, the HUN-REN Welcome Home and Foreign Researcher Recruitment Programme KSZF-144/2023. Detector construction and testing was completed within the Vesztergombi Laboratory for High Energy Physics (VLAB) at HUN-REN Wigner RCP. Authors’ contributions LO, TO, HKMT, DV organized and conducted muon monitoring. LO conducted data analysis. LO, HN, HKMT interpreted the data. LO wrote the text and prepared the figures. All authors read and approved the manuscript. Acknowledgements The technical support provided by the members of the REGARD group is gratefully acknowledged. Author Details 1 Institute for Particle and Nuclear Physics, HUN-REN Wigner Research Centre for Physics, Hungarian Research Network, 29-33 Konkoly-Thege Miklós Str., Budapest, 1121, Hungary. 2 International Virtual Muography Institute (VMI), Tokyo, Japan. 3 Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan. 4 Earthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032, Japan Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. References Aizawa K, Kanda W, Ogawa Y, Iguchi M, Yokoo A, Yakiwara H, Sugano T (2011) Temporal changes in electrical resistivity at Sakurajima volcano from observations. J Volcanol Geotherm Res199:165-175. https://doi.org/10.1016/j.jvolgeores.2010.11.003 Battaglia M, Segall S (2004) The Interpretation of Gravity Changes and Crustal Deformation in Active Volcanic Areas. 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Nat Commun 5:3381. https://doi.org/10.1038/ncomms4381 Tanaka HKM (2019) Japanese volcanoes visualized with muography. Phil Trans Roy Soc A 377:20180142. https://doi.org/10.1098/rsta.2018.0142 Tanaka HKM, Bozza C, Bross A, Cantoni E, Catalano O, Cerretto G, Giammanco A, Gluyas J, Gnesi I, Holma M, Kin T, Lázaro Roche I, Leone G, Liu Z, Lo Presti D, Marteau J, Matsushima J, Oláh L, Polukhina N, Ramakrishna SSVS, Sellone M, Shinohara AH, Steigerwald S, Sumiya K, Thompson L, Tioukov V, Yokota Y, Varga D (2023). Muography. Nat Rev Methods Primers 3:88. https://doi.org/10.1038/s43586-023-00270-7 Tang A, Horton-Smith G, Kudryavtsev VA, Tonazzo A (2006) Muon simulations for Super-Kamiokande, KamLAND, and CHOOZ. Phys. Rev. D 74:053007.https://doi.org/10.1103/PhysRevD.74.053007 The European Space Agency (ESA) (2023) SAR instrument. https://sentinels.copernicus.eu/web/sentinel/technical-guides/sentinel-1-sar/sar-instrument Uhira K, Takeo M (1994) The source of explosive eruptions of Sakurajima volcano, Japan. Journal of Geophysical Research: Solid Earth 99:17775-17789. https://doi.org/10.1029/94JB00990 Varga D, Nyitrai G, Hamar G, Galgóczi G, Oláh L, Tanaka HKM, Ohminato T (2020) Detector developments for high performance muography applications. NIMA 958:162236. https://doi.org/10.1016/j.nima.2019.05.077 Supplementary Files graphicalabstractlandscape.jpg Cite Share Download PDF Status: Published Journal Publication published 24 Dec, 2025 Read the published version in Earth, Planets and Space → Version 1 posted Reviewers agreed at journal 14 May, 2025 Reviewers invited by journal 13 May, 2025 Editor assigned by journal 09 May, 2025 First submitted to journal 08 May, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-6573242","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":455874675,"identity":"02c45018-34b5-4c63-aea6-0794ba8167fa","order_by":0,"name":"László Oláh","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7UlEQVRIiWNgGAWjYDACdgY2BoYCMIPxAYMBWIwNvxZmkAIDMIPZgGQtbBJQMfxa+JmZnwHdY2cv38x8rJqnoDaPX/oA22MePFokm9nMge5JTmxsZku7zWNwvFiyL4HdGJ8Wg8MMZhIMBswJzMw8ZrdzDI4lbjjDwCaNXwv7N6CWens2oJZikJb9hLXwgGw5zNgD1MKcY1CTuIGHgBbJZp4yiQSD44kzmNmSpf8YHEiccYaxTXIOHi387O3bJD5UVNvLtzcf/DjjT11ifw/zMYk3eLSAQQKCeRiIGRsIaUABdSSpHgWjYBSMgpEBAP7bO0gMWTEKAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-4300-8331","institution":"HUN-REN Wigner RCP","correspondingAuthor":true,"prefix":"","firstName":"László","middleName":"","lastName":"Oláh","suffix":""},{"id":455874676,"identity":"11d3efbd-af13-4ba4-96fb-42b2dee5bcb5","order_by":1,"name":"Haruhisa Nakamichi","email":"","orcid":"","institution":"Disaster Prevention Research Institute, Kyoto University","correspondingAuthor":false,"prefix":"","firstName":"Haruhisa","middleName":"","lastName":"Nakamichi","suffix":""},{"id":455874677,"identity":"9c393419-8ac6-4ae7-97aa-bb254abf74b4","order_by":2,"name":"Takao Ohminato","email":"","orcid":"","institution":"Earthquake Research Institute, The University of Tokyo","correspondingAuthor":false,"prefix":"","firstName":"Takao","middleName":"","lastName":"Ohminato","suffix":""},{"id":455874678,"identity":"da3001a9-e6f3-4de6-be8b-b070e19d0fe9","order_by":3,"name":"Hiroyuki K. M. Tanaka","email":"","orcid":"","institution":"Earthquake Research Institute, The University of Tokyo","correspondingAuthor":false,"prefix":"","firstName":"Hiroyuki","middleName":"K. M.","lastName":"Tanaka","suffix":""},{"id":455874679,"identity":"a2d0d4fd-eb98-4b49-a9f5-d6c06b34ed8e","order_by":4,"name":"Dezső Varga","email":"","orcid":"","institution":"HUN-REN Wigner RCP","correspondingAuthor":false,"prefix":"","firstName":"Dezső","middleName":"","lastName":"Varga","suffix":""}],"badges":[],"createdAt":"2025-05-01 16:32:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6573242/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6573242/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s40623-025-02325-3","type":"published","date":"2025-12-24T15:58:18+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82817500,"identity":"2b8c7540-182d-4b97-bcf1-4c4ad6f6e32e","added_by":"auto","created_at":"2025-05-15 14:36:23","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":417227,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea,b,c\u003c/strong\u003e Eruption frequencies are shown on a monthly basis for the three active craters of Sakurajima volcano, namely Minamidake A, Minamidake B and Showa. \u003cstrong\u003ed\u003c/strong\u003e A map of the measurement site is shown with topography Sakurajima volcano (GSI 2024) and our experimental settings. Vertical uplifts were monitored by InSAR (ESA 2023) at the locations highlighted with yellow crosses. PQ line shows a slice that was selected across the crater region. O indicates the location of Sakurajima Muography Observatory at longitude of 31.557° and latitude of 130.650°. Black arrow indicates the orientation of muographic observation instruments. The inner map (Natural Earth 2024) shows the location of our experiment at Sakurajima volcano in Kagoshima Bay, Kyushu, Japan.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6573242/v1/2c10b252b247ebc6ae5646ae.jpg"},{"id":82819049,"identity":"d8317e6e-b220-437f-85ee-86ee549b14b6","added_by":"auto","created_at":"2025-05-15 14:52:23","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":41304,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e The schematic drawing of Mogi modeling shows a spherical pressure source with the radius \u003cem\u003er\u003c/em\u003e at \u003cem\u003eD\u003c/em\u003e depth. The \u003cem\u003eΔV\u003c/em\u003e volume change of the Mogi source causes \u003cem\u003eU\u003c/em\u003e\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e vertical deformation on the surface of volcanic edifice at an \u003cem\u003eR\u003c/em\u003e radial distance.\u003cstrong\u003e b \u003c/strong\u003eThe vertical uplift is plotted as a function radial distance from the deformation source. Black line indicates the optimal U\u003csub\u003ev\u003c/sub\u003e(R) curve. Yellow dots show the experimental vertical ground deformation data as a function of radial distance.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6573242/v1/f84f005f5b57ea20956336a5.jpg"},{"id":82817503,"identity":"40181afd-a791-418b-ad34-3b8b6470a6ca","added_by":"auto","created_at":"2025-05-15 14:36:23","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":253016,"visible":true,"origin":"","legend":"\u003cp\u003eThe density images of the crater region of Sakurajima volcano are shown for a period from 1 October 2020 to 28 February 2024. Each image was produced using data collected throughout six months. A solid line indicates the cross-section of volcanic edifice along the PQ line of Figure 1d. Black rectangles designate the selected regions beneath the craters Minamidake A (A), Minamidake B (B) and Showa (S), respectively.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6573242/v1/9f1fabaede4e61a903671a5e.jpg"},{"id":82818505,"identity":"0a4bef09-1b8e-4335-9ad0-e2f39566c49a","added_by":"auto","created_at":"2025-05-15 14:44:23","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":384630,"visible":true,"origin":"","legend":"\u003cp\u003eThe time evolution of the parameters of ground deformation source determined by Mogi modeling for the period from April 2021 to April 2023. \u003cstrong\u003ea\u003c/strong\u003e The volume change of the deformation source versus time is shown. \u003cstrong\u003eb\u003c/strong\u003e Longitude of ground deformation source versus time. \u003cstrong\u003ec\u003c/strong\u003e Latitude of ground deformation source versus time. Eruption frequency of Minamidake A and B craters are respectively shown by blue and green boxes. \u003cstrong\u003ed\u003c/strong\u003e Variation of the depth of the deformation source from the floor of Showa crater over time. Eruption frequency of Showa crater is also shown by yellow boxes. \u003cstrong\u003ee\u003c/strong\u003e Combination of panels (c) and (d) are shown together. Black lines show the shape of Sakurajima volcano along the PQ line of Fig. 1d. Black rectangles indicate the three crater regions that were monitored by muography.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6573242/v1/5975025b57dcd1833cbc4e43.jpg"},{"id":82818509,"identity":"9dacc0ea-3fef-427b-9323-1640897fba67","added_by":"auto","created_at":"2025-05-15 14:44:23","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":95758,"visible":true,"origin":"","legend":"\u003cp\u003eThe time series of total masses across the three active crater regions of Sakurajima volcano. The mass values (black dots) are shown with 1 standard deviation error bars from January 2020 to January 2024. The dots refer to the midsts of time intervals. The coloured boxes show the monthly number of eruptions for the Minamidake A (blue boxes), Minamidake B (green boxes) and Showa (yellow boxes) craters. \u003cstrong\u003ea\u003c/strong\u003e The total masses are shown for the region beneath Minamidake A crater. \u003cstrong\u003eb\u003c/strong\u003e The total masses are shown for the region beneath the Minamidake B crater. \u003cstrong\u003ec\u003c/strong\u003e The total masses are shown for the Showa crater.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6573242/v1/6a3b121773f078b7b5560040.jpg"},{"id":99172492,"identity":"5cd86035-a085-4740-be97-1ea6085e4a87","added_by":"auto","created_at":"2025-12-29 16:10:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1868605,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6573242/v1/ee181c89-09bc-4dbf-80a8-e554f0ac0182.pdf"},{"id":82817505,"identity":"0711a5dc-56b5-40bb-ba1b-ca8644179412","added_by":"auto","created_at":"2025-05-15 14:36:23","extension":"jpg","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":229687,"visible":true,"origin":"","legend":"","description":"","filename":"graphicalabstractlandscape.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6573242/v1/ab74aa593e508e5c6a7779c8.jpg"}],"financialInterests":"","formattedTitle":"Magma migration beneath the active craters of Sakurajima volcano before the 2023 eruption of Showa crater inferred from ground deformation and muon monitoring","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIntegration of complementary geophysical, geochemical and petrological observations may allow us to explore the magma plumbing system, to study the volcanic processes that generate magma movements and to elucidate how magma intrusion affects volcano deformation, eruption dynamics, etc. (Sparks et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Magee et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Monitoring the spatio-temporal evolution of magma has successfully been applied for determining the spread of volcanic edifice (Donnadieu et al. 2001a, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2001b\u003c/span\u003e), localizing the onset of impending eruptions (D\u0026rsquo;Auria et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Cannav\u0026oacute; et al. 2015), revealing the open of new fissures (Pagli et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), and assessing the occurrence of flank failures (Cervelli et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Bonforte et al. 2015) and possible secondary effects of these hazards, such as tsunamis (Cervelli et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2002\u003c/span\u003e) or pyroclastic density currents (Belousov et al. 2020) that can affect even distant areas and result in more devastation.\u003c/p\u003e \u003cp\u003eInterferometric Synthetic Aperture Radar (InSAR) allows the detection of magma accumulation and tracking magma migration (Biggs et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). InSAR measures either pre-eruptive inflation of ground surface due to magma intrusion (Patan\u0026eacute; et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) or syn-eruptive deflation of the volcanic edifice due to release of volcanic ejecta (Massonnet et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). InSAR can be applied even at remote, inaccessible volcanic edifices. Modeling allows to create a linkage between subsurface deformation sources and the measured surface deformation: helps to interpret ground surface deformations and determine the position, volume and pressure changes of magmatic ground deformation sources (e.g., Mogi \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1958\u003c/span\u003e; McTigue \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Lisowski \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Compiling global InSAR data sets and interpreting ground deformation and other monitoring data allowed to reveal some limitations of InSAR: (A) About half of volcano deformations followed by eruptive activities and less than one-tenth of volcanoes erupted without precursory ground surface deformations (Biggs et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2014\u003c/span\u003e, Reath et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). (B) The ground surface deformations are indirect effects of subsurface phenomena, e.g., dormant craters can also uplift due to inflation source located beneath the adjacent crater on multi-vent volcanoes (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). (C) Elastic models can not distinguish whether the effects on the intrusion are caused by pressure change or magma recharge (Fern\u0026aacute;ndez et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). (D) Modeling is sensitive to the presence of weak materials within the caldera (Masterlark \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2007\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eApplying mass density sensitive complementary techniques, such as gravimetry (e.g., Fern\u0026aacute;ndez et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Battaglia \u0026amp; Segall 2004; Poland et al. 2023) or muography (e.g., Tanaka et al. 2019, \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Gibert et al \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Macedonio et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), not only contributed to revealing the aforementioned limitations, but these may help to distinguish whether ground deformations are caused either pressure changes or mass movements (Fern\u0026aacute;ndez et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Ol\u0026aacute;h et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Muography is based on the measurement of the yield of cosmic-ray muon particles. Muons are naturally occurring elementary particles created at 10\u0026ndash;15 km altitude in Earth\u0026rsquo;s atmosphere as the end product of particle physics processes induced by collisions of primary cosmic-rays with the atmospheric nuclei. Muography allows remote, passive and high-resolution scanning of the internal structure of large-sized structures, including volcanic edifices. The finite yield of muons (10,000 per square meter per minute at sea level) is reduced with 3\u0026ndash;4 orders of magnitudes after penetrating rocks with a thickness of a few hundreds of meters, thus the applicability of muography is limited for the craters and upper conduits of volcanoes. Magmatic materials have already been imaged and monitored by muography. Tanaka et al. (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) observed the uprise of magma in the conduit of Satsuma-Iwojima volcano during the 2013 eruption. Kusagaya \u0026amp; Tanaka (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) revealed a dense region in Usu volcano that was interpreted as a past magma intrusion. Joint inversion of muographic and gravimetric data revealed an intruded magma body with cylindrical shape in Showa-Shinzan lava dome (Nishiyama et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Multi-directional muography explored highly welded vent of the scoria cone and three-directional radial dikes extending from the central vent in Omuro-yama scoria cone (Nahagara et al. 2022). A magmatic body was visualized in the summit of Puy de D\u0026ocirc;me volcano (Portal et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). We imaged plug formation (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), explained a linkage between ground surface deformation and eruption frequency (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and explored the conduit structure (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) in Sakurajima volcano, Japan.\u003c/p\u003e \u003cp\u003eSakurajima volcano is supplied with magma from the Aira caldera located in Kagoshima Bay and its southern peak is erupting from three craters, namely Minamidake A, Minamidake B and Showa. The type of eruptive activity is primarily Vulcanian (Gabellini et al. 2023). Eruption mechanism has been understood (Uhira et al. 1994; Iguchi 2011, 2013; Kazahaya et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Different parts of the plumbing system have already been explored: Continuous magnetotelluric observations revealed electrical resistivity changes due to movement of mixture of magma and ground water around the sea level (Aizawa et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Absolute gravity measurements reconstructed the possible altitude of the magma head between 400 m and 800 m altitudes above sea level (ASL) (Okubo et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Vent radii of Showa was estimated to 30\u0026ndash;50 m from infrasound data (Muramatsu et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The hypocenters of the earthquakes associated with explosive eruptions are estimated to be at the depth of 500 m beneath the active craters by the seismic structure of the artificial seismic experiment (Nishimura et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Muographically measured mass density changes allowed to infer to a branched connection between the Minamidake B and Showa craters (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In recent years, the eruptive frequency was observed typically a few tens of eruptions per month with a few dormant periods (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea-c). Minamidake A and Minamidake B erupted in recent years and the Showa activated from 8 February to 4 August 2023. In this work, we analyse ground surface deformation and muon monitoring data to track the possible precursory magma migration before the eruption sequence 2023 of Showa crater and infer the structure of the plumbing system.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"2. Data collection and analysis methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Experimental setting and data collection\u003c/h2\u003e \u003cp\u003eGround surface deformation of the volcanic edifice and the yield of cosmic-ray muons across the region of active craters were measured to observe simultaneously and interpret together both deep and shallow signals of volcanic activities. Our experimental setting is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed. Vertical displacements of the southern peak around the active craters were determined using the Phased Array type C-band Synthetic Aperture Radar images acquired by Sentinel-1 (The European Space Agency 2022) with a periodic time of 12 days (NEC \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). NEC Corporation analyzed the InSAR images independently from this work and provided the vertical uplift data (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The vertical displacements were determined relative to the ground level measured on 6 April 2021 at 150 locations for the period from April 2021 to April 2023. The yield of cosmic-ray muons was monitored across the southern peak of Sakurajima volcano with the Multi-Wire Proportional Chamber (MWPC)-based Muography Observation System (MMOS) of Sakurajima Muography Observatory (Ol\u0026aacute;h et al \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The MMOS is a modular system that is operated with ten tracking system modules at longitude of 31.557\u0026deg; and latitude of 130.650\u0026deg; at a distance of approx. 2,800 m from the active craters of Sakurajima volcano at 150 m ASL. The MMOS has already been presented extensively in Refs. (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2018\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Varga et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). We conducted data collection continuously between 1st October 2020 and 31th March 2023. Collection of muographic data has been stopped once per year when maintenance of MMOS was conducted.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Mogi modeling of ground surface deformations\u003c/h2\u003e \u003cp\u003eGround surface deformations were localized near the peak region around the active craters which hinted that the source of deformations may be located near the surface of the volcanic edifice. We localized the deformation source via quantifying the volume change (\u003cem\u003eΔV\u003c/em\u003e), depth (\u003cem\u003eD\u003c/em\u003e), longitude and latitude coordinates by Mogi modeling of vertical displacements (\u003cem\u003eU\u003c/em\u003e\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e) (Mogi \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1958\u003c/span\u003e; McTigue \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Lisowski \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea visualizes a magma body as a small spherical pressure source of ground surface deformations. The magma body has an \u003cem\u003er\u003c/em\u003e radius that is significantly smaller than its \u003cem\u003eD\u003c/em\u003e depth. The surface displacement occurs in radial directions due to pressure change in the small spherical volume. The vertical component of ground surface deformation (\u003cem\u003eU\u003c/em\u003e\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e) at an \u003cem\u003eR\u003c/em\u003e radial distance from the the deformation source is expressed by the following equation:\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eU\u003c/em\u003e \u003csub\u003e \u003cem\u003ev\u003c/em\u003e \u003c/sub\u003e \u003cem\u003e= 3 ΔV D / [ 4π ( R\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;\u003cem\u003e+\u0026thinsp;D\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e \u003cem\u003e)\u003c/em\u003e\u003csup\u003e\u003cem\u003e3/2\u003c/em\u003e\u003c/sup\u003e \u003cem\u003e] .\u003c/em\u003e (1)\u003c/p\u003e \u003cp\u003eParameter estimation procedure based on grid searching via minimizing the relative difference between the measured and modeled vertical uplifts (\u003cem\u003eU\u003c/em\u003e\u003csub\u003e\u003cem\u003ev\u003c/em\u003e\u003c/sub\u003e) of ground surface as a function of the lateral distance of measurement point from the deformation source (\u003cem\u003eR\u003c/em\u003e). Four model parameters were varied: the \u003cem\u003eΔV\u003c/em\u003e volume change, the longitude coordinate, latitude coordinate and \u003cem\u003eD\u003c/em\u003e depth from the level of the crater floor. The measured vertical uplift data were considered for altitudes above 700 m ASL for this analysis. The \u003cem\u003eΔV\u003c/em\u003e volume change was varied from 30 Mm\u003csup\u003e3\u003c/sup\u003e to 50 Mm\u003csup\u003e3\u003c/sup\u003e with a step size of 5 Mm\u003csup\u003e3\u003c/sup\u003e. The longitude and latitude coordinate was respectively set to different values in a range from 130.658\u0026deg; to 130.660\u0026deg; and from 31.579\u0026deg; to 31.581\u0026deg;. The step size was set 0.00025\u0026deg; and 0.00050\u0026deg; for the longitude and the latitude, respectively. The \u003cem\u003eD\u003c/em\u003e depth from the crater floor was varied from 100 m to 1000 m with a step size of 25 m. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb shows an example for comparison of vertical uplifts versus radial distance from source location for experimental (yellow-coloured dot) data set and for the Mogi modelling (black solid line).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Muon data analysis and modeling\u003c/h2\u003e \u003cp\u003eEvent-by-event analysis procedure has been presented extensively in Ref. (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Here we describe the analysis procedure in a nutshell. The procedure is initiated with reconstruction of clusters of muon hits on chamber by chamber. This reconstruction determined the cluster\u0026rsquo;s centroids, sizes and numbers. Thereafter, a combinatorial algorithm gathered the cluster centroids into track candidates and ordered them based on the goodness of line fit (chi-square per number of degrees of freedom, \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e/ndf\u003c/em\u003e, where the \u003cem\u003endf\u003c/em\u003e equals to number of detectors minus two), and selected the best fitting track candidate with the smallest \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e/ndf\u003c/em\u003e. In the last step, a track count histogram with a bin size of 0.023 in both directions was filled based on the horizontal and vertical slopes of tracks. After filling the track count histogram, flux was calculated for each angular bin by dividing the track counts with sensitive surface area, solid angle and effective measurement time. Statistical flux error was determined by dividing the square root of track counts with the same quantities. Forward modelling of flux was conducted to determine the density across the volcanic edifice. The modeled flux was determined with different density-lengths (density integrated over path-length) by integrating the energy and elevation angle dependent spectra of muons (Tang et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) from threshold energies that are required for muons to penetrate the given density-lengths (Groom et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Path-lengths were calculated using the digital elevation model of the edifice (Geospatial Authority of Japan 2024). The density value was extracted when the difference between the measured and modeled muon fluxes was found to be minimal. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the densities for the measurement period with a bin size of 0.023 in both horizontal and vertical direction. This bin size corresponds to a spatial resolution of about 60 m from the distance of 2,800 m. The mass (\u003cem\u003em\u003c/em\u003e) was calculated for each region by summing up the masses that were quantified as follows.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003em = \u0026sum;\u003csub\u003ei\u003c/sub\u003e ρ\u003csub\u003ei\u003c/sub\u003e ✕ T\u003csub\u003ei\u003c/sub\u003e ✕ D\u003csup\u003e2\u003c/sup\u003e ✕ Δtan(θ\u003csub\u003ex\u003c/sub\u003e) ✕ Δtan(θ\u003csub\u003ey\u003c/sub\u003e), (2)\u003c/p\u003e \u003cp\u003ewhere \u0026sum; runs over the pixels within the selected region, ρ\u003csub\u003ei\u003c/sub\u003e is the density in pixel i, T\u003csub\u003ei\u003c/sub\u003e is the thickness along pixel i, D is the distance of 2,800 m between the SMO and volcanic edifice, Δtan(θ\u003csub\u003ex\u003c/sub\u003e) and Δtan(θ\u003csub\u003ey\u003c/sub\u003e) are respectively the horizontal and vertical pixel sizes.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Tracking deep magma migration by modeling ground deformation source\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows respectively the variations of the modeled parameters (black circles connected with solid lines) of Mogi source from April 2021 to April 2023 and the eruption frequencies of active craters (coloured boxes) from January 2021 to December 2023. The volume change of the Mogi source was found to be about 30,000\u0026ndash;40,000 m\u003csup\u003e3\u003c/sup\u003e during the entire period (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). The source kept its latitude within a range of 31.579\u0026deg;-31.581\u0026deg;, i.e., it moved neither to north nor to south throughout the measurement period from beneath the active craters (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). The variations of longitude coordinate indicate that the source of ground deformation shifted from the region located beneath Minamidake A crater to a region located beneath Minamidake B and Showa crater from April 2021 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). This horizontal movement may resulted in the shift of eruptive activity from Minamidake A (blue boxes) to Minamidake B (green boxes). Throughout the entire measurement period, the Mogi source uplifted from 700 m depth (sea level) to 330 m depth (370 m ASL) relative to the level of Showa crater\u0026rsquo;s floor (700 m ASL) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). Since the latitude of the Mogi source remained within a narrow range, we combined the longitudinal and the vertical variations of the Mogi source in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee. Here the horizontal coordinates are shown relative to the observation axis (black arrow of Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed) of the muography observation instrument. The depth is measured relatively to the floor of Showa crater. The shape of crater floors (black solid line) were extracted along the PQ line of Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed. Two phases are indicated for the movement of the Mogi source: (1) a rapid horizontal shift between the Minamidake A and Minamidake B occurred in 2021 and (2) a slower uplifting. The eruption sequence of Showa crater started when the source reached the depth of about 350 m (350 m ASL) in February 2023 (yellow boxes in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Muon monitoring of shallow material transfers\u003c/h2\u003e \u003cp\u003eWe conducted off-line analysis of muographic data (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The analysis procedures are presented in a nutshell in section Methods. In this work, we reconstructed the mass density images across the crater region and determined the total mass beneath the active craters. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea-\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec show the 6 month average (arithmetic mean values) of masses with one standard deviation (black dots with error bars) for the regions beneath Minamidake A, Minamidake B, and Showa craters (black rectangles in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee) and the monthly number of eruptions (colored boxes) from January 2021 to January 2024. Simultaneous changes were observed in the masses from January 2021 to March 2022: the total mass decreased beneath Minamidake A and Minamidake B with about 10\u0026ndash;15 Mt and increased beneath Showa with about 8 Mt. Throughout the same period, the eruptive activity shifted from Minamidake A (blue boxes) to Minamidake B (green boxes). The masses did not change beneath the craters during a relatively dormant period from March 2022 to May 2022. The masses increased beneath Minamidake A, Minamidake B and decreased beneath Showa crater during the eruptive activities of the former two craters from May 2022 to October 2022. From November 2022 to May 2023, the mass started to decrease beneath Minamidake A and Minamidake B until the end of their eruption episodes and the mass increased beneath Showa crater. Between May 2023 and August 2023, the mass decreased beneath Showa crater until the end of the eruption sequence. During the same period, the masses increased beneath the dormant Minamidake A and Minamidake B craters. After the end of the eruption sequence in August 2023, the mass did not change beneath the Showa crater. Besides the crater regions the average mass was monitored across a reference region in which volcanism did not occur and the mass did not change here during the entire data collection period (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion and conclusions","content":"\u003cp\u003eJoint observation of Sakurajima volcano has been conducted with ground deformation and muon monitoring. Ground deformation source was modeled for tracking the deep processes. Muography was conducted for monitoring the mass changes across the shallow regions of volcanic edifice. The finite yield of muons allowed the imaging of the upper 120 m parts of conduits and craters of Sakurajima volcano during the measurement periods of 6 months. The mass sensitivity of muography allowed (1) to localize the ground deformation source of the uplift more in a pin-point way than InSAR, e.g., in a previous work the ground deformation data showed uplift in the region of Showa Crater but it was caused by the magma located beneath Minamidake Crater (Ol\u0026aacute;h et al \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), and (2) helped to distinguish between the pressure change induced or mass intrusion induced ground deformations. Although muography could not pin-point the source of ground deformation in these regions, the mass changes due to compressions and decompressions in mixture of gaseous and liquid materials beneath the volcanic plug could be quantified and shallow volcanic processes could be studied more accurately. The observational results are discussed together for the following periods as follows.\u003c/p\u003e \u003cp\u003eFrom January 2021 to March 2022 a lateral movement of ground deformation source occurred at a depth of 600\u0026ndash;700 m beneath the floor of Showa crater. During the same period, the mass changes were respectively observed beneath the two Minamidake craters and the Showa crater to -10-15 Mt and +\u0026thinsp;8 Mt that also indicates material transfer towards Showa crater. Our interpretation is that the observed material transfers resulted in the shift of eruptive activities from Minamidake A (blue boxes in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec) to Minamidake B (green boxes in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). The depth of lateral movement of the ground deformation source was found to be consistent with the depth of a fracture network reconstructed with magnetotelluric (MT) measurements conducted at 3.3 km east and 3 km west from Minamidake crater in 2008\u0026ndash;2009 (Aizawa et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The resistivity increased around sea level beneath the eastern measurement site in coincidence with the volcanic unrest. This resistivity increase was interpreted as a sign of lateral degassing of volatiles from a magma body. The results suggested the presence of a fracture network at a depth around sea level in which a mixture of ground water and degassed volatiles can migrate laterally. Results of ground deformation source modeling also support the presence of this lateral fracture network.\u003c/p\u003e \u003cp\u003eDuring the eruption sequences of Minamidake B and Minamidake A craters occurred from May 2022 to October 2022, the masses increased with about 15 Mt beneath Minamidake A, Minamidake B and decreased with about 10 Mt beneath Showa crater. These trends suggest material transfer from a shallow region beneath Showa crater to a shallow region beneath Minamidake craters. Magma intrusion may caused the remaining mass increase.\u003c/p\u003e \u003cp\u003eDuring the period from November 2022 to May 2023, mass started to decrease beneath Minamidake A and Minamidake B until the end of their eruption episodes and densities increased beneath Showa crater. Eruptive activities started in the Showa crater in February 2023 when the ground deformation source rose to the depth of about 350 m beneath the bottom of Showa crater (350 m ASL). These observations suggest that the Showa crater activates when the magma reaches a sufficiently shallow depth beneath the active craters. This is similar to what was observed before earlier eruption episodes of Showa crater when the magma head was quantified between 400 m and 800 m ASL by the absolute gravity measurements (Okubo et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). It is worth to note that the difference between the altitude of current floor level and earlier reconstructed source altitude originates from deepening and widening of Showa crater (Japan Meteorological Agency \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBetween May 2023 and August 2023, the mass decreased with 10 Mt beneath Showa crater until the end of the eruption sequence. We interpret this mass decrease as decrease in magma feeding and release of volcanic ejecta. Former one resulted in the stop of eruptive activity. This is consistent with our earlier observations for the active Mindamidake craters (Ol\u0026aacute;h et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eObserving a mass transfer between the active craters at shallow depth and activation of Showa crater as ground deformation source reach shallow depths of below 350 m support the presence of a common shallow magma storage and conduit system beneath the three craters. Seismic sources of explosive eruptions are located in and around a region at a depth of 400 m (Nishimura et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Furthermore, geochemical analysis of samples from ejected rocks indicated that these rock samples are identical and originate from the same source (Matsumoto et al. 2023). Similar structure was observed at Mt. Etna in which short-term magma storage occurred close to the surface before a flank eruption and summit eruptive activity from a source located at larger depth (Sanderson \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1982\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eJoint analysis of ground deformation and muon data improves reliability of the monitoring of shallow parts of volcano\u0026rsquo;s plumbing system and may allow more robust assessment of impending eruption sequences of Showa crater.\u003c/p\u003e "},{"header":"Abbrevations","content":"\u003cp\u003eASL Above Sea Level\u003c/p\u003e \u003cp\u003eInSAR Interferometric Synthetic Aperture Radar\u003c/p\u003e \u003cp\u003eMMOS MWPC-based Muography Observation System\u003c/p\u003e \u003cp\u003eMT Magnetotelluric\u003c/p\u003e \u003cp\u003eMWPC Multi-Wire Proportional Chamber\u003c/p\u003e \u003cp\u003endf Number of Degrees of Freedom\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Integrated Program for the Next Generation Volcano Research, the Joint Usage Research Project (JURP) of the University of Tokyo, Earthquake Research Institute, University of Tokyo (ERI) under project ID 2023-H-03, the Hungarian NKFIH research grant under identification number TKP2021-NKTA-10, the HUN-REN Welcome Home and Foreign Researcher Recruitment Programme KSZF-144/2023. Detector construction and testing was completed within the Vesztergombi Laboratory for High Energy Physics (VLAB) at HUN-REN Wigner RCP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contributions\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;LO, TO, HKMT, DV organized and conducted muon monitoring. LO conducted data analysis. LO, HN, HKMT interpreted the data. LO wrote the text and prepared the figures. All authors read and approved the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The technical support provided by the members of the REGARD group is gratefully acknowledged.\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003cstrong\u003eAuthor Details\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eInstitute for Particle and Nuclear Physics, HUN-REN Wigner Research Centre for Physics, Hungarian Research Network, 29-33 Konkoly-Thege Miklós Str., Budapest, 1121, Hungary. \u003csup\u003e2\u003c/sup\u003eInternational Virtual Muography Institute (VMI), Tokyo, Japan. \u0026nbsp;\u003csup\u003e3\u003c/sup\u003eDisaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan. \u003csup\u003e4\u003c/sup\u003eEarthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo, 113-0032, Japan\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAizawa K, Kanda W, Ogawa Y, Iguchi M, Yokoo A, Yakiwara H, Sugano T (2011) Temporal changes in electrical resistivity at Sakurajima volcano from observations. 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NIMA 958:162236. https://doi.org/10.1016/j.nima.2019.05.077\u003c/li\u003e\n\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":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"earth-planets-and-space","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"epsp","sideBox":"Learn more about [Earth, Planets and Space](http://earth-planets-space.springeropen.com)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/epsp/default.aspx","title":"Earth, Planets and Space","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Muography, cosmic-ray muon, InSAR, ground deformation, volcano, magma, conduit","lastPublishedDoi":"10.21203/rs.3.rs-6573242/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6573242/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eGround deformation source modeling and muographic mass density monitoring were applied for studying the plumbing system of Sakurajima volcano, Kyusu Japan using data collected by Interferometric Synthetic Aperture Radar and Sakurajima Muography Observatory. Lateral movement of ground deformation source was observed to east beneath the active craters around sea level that resulted in the shift of eruption frequency between the Minamidake craters. During the same period, muography showed opposite trends in mass changes for adjacent craters: mass decreased beneath the Minamidake A crater and Minamidake B craters and mass increased beneath the Showa crater that also suggests the lateral movements of materials towards east. Thereafter, the ground deformation source started to rise and the eruption sequence of Showa crater started when the deformation source reached a depth of about 350 m. The muographically measured mass increased beneath Showa crater before the start of the eruption sequence. During eruption episodes of Minamidake A and B craters the mass did not change beneath these craters and decreased beneath Showa crater that suggest a connection between the adjacent craters. These observations suggest the presence of a deep magma channel around sea level which feeds Minamidake A and Minamidake B craters and the existence of a shallow magma chamber about 350 m beneath the active craters which feeds all craters. Joint measurement of ground surface deformations and cosmic-ray muons allows simultaneous monitoring of deep and shallow volcanic processes that may allow more reliable assessment of impending eruption sequences of Showa crater of Sakurajima volcano.\u003c/p\u003e","manuscriptTitle":"Magma migration beneath the active craters of Sakurajima volcano before the 2023 eruption of Showa crater inferred from ground deformation and muon monitoring","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-15 14:36:18","doi":"10.21203/rs.3.rs-6573242/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-05-14T06:56:05+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-13T09:57:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-10T01:26:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"Earth, Planets and Space","date":"2025-05-09T01:20:55+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"earth-planets-and-space","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"epsp","sideBox":"Learn more about [Earth, Planets and Space](http://earth-planets-space.springeropen.com)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/epsp/default.aspx","title":"Earth, Planets and Space","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c104e047-0faa-49ee-868f-f0112cf5e6d7","owner":[],"postedDate":"May 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-29T16:06:05+00:00","versionOfRecord":{"articleIdentity":"rs-6573242","link":"https://doi.org/10.1186/s40623-025-02325-3","journal":{"identity":"earth-planets-and-space","isVorOnly":false,"title":"Earth, Planets and Space"},"publishedOn":"2025-12-24 15:58:18","publishedOnDateReadable":"December 24th, 2025"},"versionCreatedAt":"2025-05-15 14:36:18","video":"","vorDoi":"10.1186/s40623-025-02325-3","vorDoiUrl":"https://doi.org/10.1186/s40623-025-02325-3","workflowStages":[]},"version":"v1","identity":"rs-6573242","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6573242","identity":"rs-6573242","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}