Tracking the temporal evolution of seismic attenuation at a volcano by using remote seismicity occurring in a seismic nest. Case: Nevado del Ruiz volcano and Bucaramanga seismic nest, Colombia

Tracking the temporal evolution of seismic attenuation at a volcano by using remote seismicity occurring in a seismic nest. Case: Nevado del Ruiz volcano and Bucaramanga seismic nest, Colombia | 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 Tracking the temporal evolution of seismic attenuation at a volcano by using remote seismicity occurring in a seismic nest. Case: Nevado del Ruiz volcano and Bucaramanga seismic nest, Colombia John Makario Londono, Beatriz Elena Galvis This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7530112/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract A seismic study was conducted on the attenuation of seismic waves in the Nevado del Ruiz Volcano (NRV) for the period January 2017-December 2024, based on remote earthquakes generated in the Bucaramanga Seismic Nest (BSN), located 320 km away at northeast of the volcano and recorded in one seismic station deployed at NRV. It was possible to observe a temporal variation in the attenuation in the NRV related to changes in its activity, due to the movement of fluids inside the volcano. An increase in attenuation was detected between 2017 and 2018 and subsequently a new, larger increase between 2022 and 2024. These changes coincide with significant variations in degassing inside the volcano detected with other instruments and techniques. A negative relationship was observed between seismic attenuation and the SO 2 flux to the atmosphere for some periods, while a positive relationship with the radiated seismic energy of seismicity associated with fluid dynamics inside the volcano was observed as well. This behavior may indicate circulating of fluids inside the NRV which accumulate inside the volcano generating higher seismic attenuation. Some of these fluids are subsequently released into the atmosphere such as SO 2 , producing a decrease in the attenuation of seismic waves at NRV. This process seems to repeat itself over time. This study suggests that seismic attenuation measured in repetitive remote earthquakes located in the NSB can be used as a new tool for volcanic seismic monitoring in Colombia. Nevado del Ruiz volcano Bucaramanga seismic nest seismic wave attenuation coda Q Volcanic tremor SO2 flux Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction One of the important tasks in disaster risk management (DRM) is risk awareness, that is, understanding the hazards to which the community is exposed, and gaining a deeper understanding of the phenomena that generate them. By knowing these hazards better, more prevention strategies can be defined, thus reducing the effects of these phenomena on the community. In the case of volcanic eruptions, it is necessary to generate early warning systems that allow authorities to prepare to deal with any potential emergency. For this reason, it is imperative to have not only robust monitoring systems, but also techniques that allow detecting changes in some parameters of volcanic activity before an impending eruption. Volcanic eruptions are one of the natural phenomena that can have the greatest impact on humanity both locally and globally. Recent large volcanic eruptions have globally affected the climate of planet Earth (e.g., Pinatubo Volcano 1991; Hunga Tonga-Hunga 2022). For this reason, it is important to be able to understand the behavior of potentially dangerous volcanoes to be better prepared for an eventual eruption. Volcanic monitoring is a fundamental task to reduce the risk of disasters due to volcanic eruption. Many techniques have been used for volcano monitoring in the last decades. The more monitoring techniques are applied to an active volcano, the greater the probability of providing a better diagnosis of its activity. For this reason, the use of new methodologies or techniques becomes a critical issue to advance in better diagnoses of volcanic activity, which contributes to better preparation of the community in general to face the effects of this type of natural phenomenon. Regarding seismicity produced by volcanic activity, it should be mentioned that it is the main manifestation of the reactivation of a volcano, since it is normally associated with the movement of magma inside the volcano. One of the most common techniques used to tracking the volcano seismicity, includes counting number of earthquakes, volcanic earthquakes classification, calculating seismic energy released, spectral content of seismic waveforms, among other parameters (Saccorotti and Lokmer, 2021 ). The recording of this seismicity allows to know important aspects of the internal structure of the volcano, as well as changes in the medium through which seismic waves travel. That is why recording seismic activity is essential for monitoring a volcano. However, sometimes the amount of seismicity necessary to make an appropriate assessment of volcanic activity is not recorded. The attenuation of seismic waves is a physical parameter that has been used previously to monitor changes in volcanic activity (Londoño and Sudo 2002 ; Moncayo et al. 2004 ; Snieder and Hagerty 2004 ; Grêt et al. 2010 ; Titzschkau et al. 2010 ) or to study its spatial distribution (Pulli 1984 ; Iyer and Dawson ). To monitor the temporal variations in seismic wave attenuation, seismicity must be generated at different locations beneath the volcano or at remote sites if tomographic 3D or 4D attenuation studies were performed (Iyer and Dawson 1993 ; Gabrielli et al. 2022 ; Guardo et al. 2022 ), or at specific sites close to the volcano if the intention were to generate time series. In the latter case, unfortunately, earthquakes are not always generated with the ideal regularity or frequency to monitor the changes in quasi-real time. Typically, a retrospective analysis of seismic activity is performed, and techniques are applied to calculate the attenuation of seismic waves a posteriori. To date, there are very few techniques or methodologies that allow monitoring changes in seismic wave attenuation in quasi-real time for volcanic monitoring because of the reasons mentioned previously. This project seeks to make up for the lack of seismicity located in volcanic areas needed for their monitoring, taking advantage of the natural repetitive seismicity that occurs in a remote seismic nest (Zarifi et al. 2007 ). With this type of natural and repetitive seismicity, it is possible to monitor distant volcanic areas. It is possible to monitor changes in the attenuation suffered by seismic waves inside the volcano, which in turn allows us to better understand the behavior of the volcano. Taking advantage of the permanent natural seismicity generated in the so-called seismic nest of Bucaramanga (Colombia) (BSN), one of the only three places in the world where permanent seismicity occurs in the same spatial location (Zarifi et al. 2007 ), it is proposed to use such a seismicity to detect quasi-real variations in the attenuation of seismic waves at seismic stations located on the Nevado del Ruiz Volcano (VNR), the most active volcano in Colombia to date (September 2025), which is in an eruptive period, characterized by minor eruptions with frequent ash emissions, affecting municipalities near the volcano, mainly located in the Department of Caldas, Tolima and Risaralda, center of Colombia. 2. Methods and data The attenuation of seismic waves can be defined in a straightforward way, as the loss of energy suffered by seismic waves when traveling through a medium or as their travel time passes. This loss of energy is reflected in a gradual decrease in the amplitude of seismic waves. Physically, the attenuation of a wave is said to be the loss of energy for each cycle. There is a portion of the seismic signal that is characterized by reflecting the effects of the path through which the seismic rays traveled, that is, the medium they passed through. This portion is called “coda waves” (Aki and Chouet 1975 ). In this way, the analysis of this portion of the seismogram (or seismic signal) allows us to extract valuable information about the medium through which the seismic waves traveled, such as how heterogeneous it is, how attenuative it is, what type of composition it may have, what level of stress it may have, among other parameters. The attenuation of seismic waves is the inverse of the medium quality factor, Q (therefore, the attenuation is Q − 1 ), which is a measure of how firm or consolidated the medium is; the more compact, rigid and homogeneous the medium is, the higher the value of Q, and vice versa. In the seismic field, the quality factor Q, measured in the coda portion of the waves, is called “coda Q.” The attenuation of seismic waves can be caused by four main factors: 1) intrinsic absorption of the medium, which has to do with the properties of the medium through which the waves travel, in particular due to the loss of energy that is converted into heat and absorbed by the medium; 2) geometric expansion, which has to do with the decrease in amplitude with distance due to the advance of seismic wave fronts; 3) anelasticity of the medium; and 4) dispersion phenomena or “scattering” of the waves due to the heterogeneities of the medium. Different models and methods have been developed to extract information from Q coda of earthquakes. Some of the most widely used methods due to their simplicity and ease of calculation are the Aki and Chouet method (1974) and the Sato’s method (1977). Both methods are based on the premise that coda waves are backscattered S waves in the medium, and that there is only one scatterer or heterogeneity in the medium between the seismic source and the receiver or seismic station. These models are called “single scattering” models. The difference between the two is that the Aki and Chouet (1974) method considers the seismic source and the receiver located at the same site in space, while the Sato’s method (1977) extended the Aki and Chouet ( 1975 ) method and considers the scatterers distributed isotropically and considers the source-receiver distance. A generalized, functional and linearized way of expressing seismic attenuation using the Sato’s method (1977) is as follows: As is the maximum amplitude of the S waves, A ( t ) is the average amplitude taken at time t and measured from the origin of the earthquake, t s is the travel time of the S wave, w is the angular frequency, C is a constant and Q is the quality factor. From the slope b it is possible to calculate Q by adjusting Eq. ( 1 ) using least squares techniques. This method for calculating Q have been applied in a large number of regions around the world and in different geological and tectonic environments (Roecker et al. 1982 ; Singh and Hermann 1983; Pulli 1985; Gusev and Lemzikob 1985 ; Phillips and Aki 1986 ; Ambeh and Fairhead 1989 ; Kvamme and Havskov 1989 ). Some studies suggest that the coda Q changes before the occurrence of earthquakes and volcanic eruptions, and that it could even be considered as a possible premonitory (Jin and Aki 1986 ; Fehler et al. 1988 ; Londono 1994 ; Tusa et al. 2004 ; Giampicolo et al. 2007 ). There is no literature available on the application of a distant or remote repetitive natural source of seismicity (seismic nest) to monitor the variation of seismic wave attenuation in a volcanic area. In this study, it is assumed that the distant seismic nest (with intermediate-depth earthquakes) behaves as a point source where repetitive earthquakes are generated, and that seismic waves (S waves) travel along the same path, given the long distance between the seismic source and the seismic stations located at the volcano. If any change in seismic wave attenuation is detected with this setting of seismic source and receivers, it is due to variations in the medium close to the stations located at volcanic area. In this study it is assumed that: 1) most the medium between the source (intermediate-depth) and the receivers does not change overtime, due basically to the fact the almost all the distance traveled by the seismic waves (backscattered S-waves) is inside the upper mantle and lower crust; 2) only the portion traveled in the upper crust close to the seismic stations change due to volcanic activity; 3) no deep magma intrusions (> 30 km depth) or another deep phenomena who changes abruptly the medium conditions occurred during the studied period. Figure 1 shows the sketch. For this study, seismic traces from the Bucaramanga seismic nest (BSN here in after), recorded in the seismic station BIS1 of the local seismic monitoring network of Nevado del Ruiz (NRV) were used for the analysis. A total of 943 high-quality (high signal to noise ratio) earthquakes with magnitudes > 3.5 were used for the calculation of coda Q, covering the period 2017–2024. Figure 2 shows the location map and the hypocenter of earthquakes used for this study (Fig. 3 ). With the aim of verifying the assumption that the seismic rays of earthquakes generated at the BSN and recorded at the NRV local seismic stations follow the same trajectory, an analysis was conducted using cross correlation coefficients between the waveforms of different earthquakes coming from the BSN at the same local seismic station of NRV. Figure 4 shows an example at the BIS1 station for some earthquakes. From this Figure it is possible to observe that the frequency spectra are very similar for the same station with an average correlation coefficient of 0.748 (0,64–0.87) for no filtered waveforms, while for those filtered waveforms in the frequency band used in this study (8–16 Hz) the correlation coefficient decreased with an average of 0.655 (0.60–0.71). This can be due to local effects of seismic attenuation as we expected, and other factors not considered in this study. We choose a fixed time window of 15 s after twice the S-wave travel time for coda Q calculation. Once the seismic attenuation was calculated at the centered band of 12 Hz (Londono and Sudo, 2001) for each seismic trace, those values were grouped, and the monthly average of the seismic attenuation was calculated. 3. Recent activity of Nevado del Ruiz volcano NRV is to date (September 2025) the most active volcano in Colombia. The reactivation started in 2010 with a small ash emission and large amounts of SO 2 released. In 2011 a large and deep source of ground deformation was detected to the SW of the volcano (Lundgren et al. 2015 ). Later, in May and June 2012, two phreatic eruptions (VEI = 1–2) took place. Between August and September 2015 evidence of a dome extrusion at the bottom of the active crater was detected (such as seismicity, ground deformation, SO2 degassing, and thermal anomalies). This dome still is emplaced at the bottom of the active crater, with observed surficial changes (Castano et al 2020). From 2015, frequent ash emissions occurred at NRV (Londono and Galvis 2018 ). In 2021 an increase in volcanic tremor intensity was detected, which ended with strong seismic activity, ash emissions, and thermal anomalies, that led to change the alert level in March 2023 to orange color, lasting for three months. After 2024, the activity of NRV decreased slightly compared to the previous years. To date (September 2025) NRV continues unstable with frequent minor eruptions. 4. Results Figure 5 shows the average monthly value of attenuation for the period analyzed January 2017-February 2024. A general oscillatory trend of attenuation over time can be observed, with increases and decreases. An increase is observed between 2017 (April) and 2018 (January). Subsequently, a decrease is observed until the beginning of 2020 (March) and then an increase in attenuation until mid-2020 (June) and from that date a general tendency to decrease is observed until mid-2022 (August). Then, a constant increase is observed until the beginning of 2023 (February) and subsequently a decrease until mid-2023 (August). The variation in attenuation ends with a slight increase from that date until the end of 2023 (October) and subsequently a decrease until early 2024 (March). To observe the relationship of the temporal variations of seismic attenuation with the activity of the VNR, a comparison of the seismic attenuation with other parameters such as the SO 2 monthly flux and the radiated seismic energy (RSE) of earthquakes associated with fluid activity (LP earthquakes and volcanic tremor, Chouet and Matoza 2013 ) was made for the analyzed period. Figures 6 and 7 show the comparisons. In Fig. 6 it can be observed that there seems to be a negative relationship with the monthly SO 2 flux, particularly for 2019 and 2021. While SO 2 flux trend seems to decrease over time, the seismic wave attenuation seems to increase at NRV during the studied period. In the case of Fig. 7 , it is possible to observe that there is no clear correlation between seismic wave attenuation and RSE of seismicity associated with fluids activity before 2021 but after middle 2021 there is a positive correlation with some shifting in time. From October 2021 to April 2022 the most intense volcanic tremor occurred since the last eruption (dome extrusion) in 2015. This event was associated with an initial increase and then a decrease in seismic wave attenuation. From November 2022 to April 2024 a general tendency of increasing in seismic wave attenuation was associated with a fluctuating variation in the RSE of tremor and other seismicity related to fluid activity inside NRV. From Fig. 8 it is possible to observe that there is no clear correlation between seismic wave attenuation and duration of volcanic tremor. Even though it is possible to observe a tendency after June 2021, like that observed in Fig. 7 , in which both parameters started to change more intensively, that is, larger values were observed in both. 5. Analysis and interpretation Seismic wave attenuation has changed over time at NRV. From seismic data coming from BSN it was possible to detect such temporal changes in the studied period (2017–2024). Those temporal changes in seismic wave attenuation can be associated with changes in SO 2 flux, RSE of seismicity associated with fluid dynamics, and duration of volcanic tremor. The SO 2 flux has decreased over time, as we mentioned previously (Fig. 6 ). One possibility is that the SO 2 is released into the atmosphere, decreasing the seismic wave attenuation beneath the NRV. On the contrary, when the release of SO 2 to the atmosphere decrease, it means that the gas is retained inside the volcano, increasing the seismic wave attenuation. It is well known that the presence of gas inside the media increases the seismic wave attenuation (Priest et al. 2006 ; Tisato et al. 2021 ; Chapman et al. 2021 ; Guo et al. 2021 ; Liu et al. 2024 ). Moreover, the increasing of RSE of seismicity associated with fluid dynamics may indicate that more fluids are available beneath the volcano. As we mentioned previously, after 2021 this was the case of NRV (Fig. 7 ), suggesting that more fluids were available in the plumbing system of NRV, yielding to increasing the seismic waves attenuation. This suggestion is supported by the fact that the duration of volcanic tremor increased after 2021, which indicates, again, that it is possible that more fluids were circulating beneath the volcano. To compare the relationship of the RSE of seismic activity related to fluids inside the volcano and the flux of SO2 to the atmosphere with the seismic wave attenuation, we plotted the monthly ratio of RSE to SO2 flux and the seismic wave attenuation (Fig. 9 ). We found that effectively in the middle of 2021 there is a change in this ratio that correlates with a general tendency to increase the seismic wave attenuation over time. This is remarkable because it corroborates that there was a real change inside the volcano related to more fluids circulating in the magmatic and/or hydrothermal system, which probably affected the seismic wave attenuation (increase). The frequency band used in this study (6–16 Hz) was previously analyzed and defined by Londono ( 1994 ) by using multiple-scattering methods as a proper band to detect changes in the fluids or temperature at NRV due to intrinsic absorption of the media, due to the coda Q values for this frequency band are very similar to those obtained for Q intrinsic (Qi), indicating that Q scattering (Qs) has less influence in this frequency band at NRV. The results of this study show the utility of the remote seismicity produced by a seismic nest to be used as an additional monitoring tool of volcanic activity providing the size of the earthquakes and the distance volcano-seismic nest are between suitable ranges to be tracked over time. In the case of BSN, there are several active volcanoes that are close enough (around 300km faraway) to allow remote seismic monitoring, such as NRV, Nevado de Santa Isabel, Cerro bravo volcano, and Cerro Machín volcano. This is the first study that uses remote seismicity produced in a natural seismic nest to monitor a volcano seismically. We focused on seismic wave attenuation monitoring (coda Q) but other seismic parameters can be monitored as well, such as P and S wave velocity, Vp/Vs ratio, among others. 6. Conclusions Seismic wave attenuation changes over time were investigated at NRV by using remote seismicity located in the BSN. We could confirm that the seismic attenuation at NRV has changed over time due to the presence of fluids inside the volcano. Fluctuations of the seismic attenuation (increase and decrease) were observed during the period analyzed. After 2022 a continuous increase in the seismic wave attenuation was observed and was related to an increase in fluids inside the volcano, which had increased particularly from 2021, evidenced by the decrease of SO 2 releasing to the atmosphere and the increase of volcanic tremor beneath the active crater. The natural occurrence of seismicity in a seismic nest can be used as an additional volcano monitoring strategy if the volcano is close enough to record those repetitive earthquakes. Declarations Acknowledgments We want to thanks to the colleagues of the volcano observatory of Manizales (OVSMA) of the Colombia Geological Survey (CGS) for providing the information of the seismic stations of the NRV, particularly to Carolina Acosta and César Vega for the seismic data format transformation. We thank the National Seismic Network of CGS for providing the seismic data set of BSN. We also thanks to the Catholic University of Manizales for supporting this research. Funding Declaration This study was funded by Universidad Católica de Manizales and Servicio Geológico Colombiano. The authors have no relevant financial or non-financial interests to disclose. Data Availability The data used in this study belongs to SGC and can be accessed by previous official request to SGC headquarters. Competing interest The authors declare that here are no Competing Interests with this study. Author contribution All authors contributed to the study conception and design. Material preparation and data collection were performed by John M Londono (JML) and Beatriz E Galvis (BEG). The first draft of the manuscript was written by JML and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. References Aki K, Chouet B (1975) Origin of coda waves: source, attenuation and scattering effects. J Geophys Res 80: 3322–3342 Ambeh WB, Fairhead JD (1989) Coda Q estimates in west Africa. Bull Seismol Soc Am 79: 1589–1600 Castaño LM, Ospina CA, Cadena OE, Galvis BE, Londono JM, Laverde CA, Kanejo T, Ichihara M (2020) Continuous monitoring of the 2015–2018 Nevado del Ruiz activity, Colombia, using satellite infrared images and local infrasound records. Earth Planets Space 72: 81. https://doi.org/10.1186/s40623-020-01197-z Chapman S, Borgomano JVM, Quintal B, Benson SM, Fortin J (2021) Seismic wave attenuation and dispersion due to partial fluid saturation: Direct measurements and numerical simulations based on X-ray CT. Journal of Geophysical Research: Solid Earth, 126, e2021JB021643. https://doi.org/10.1029/2021JB021643 Chouet B, Matoza R (2013) A multi-decadal view of seismic methods for detecting precursors of magma movement and eruption. J Volc Geoth Res 252: 108-175. https://doi.org /10.1016/j.jvolgeores.2012.11.013 Gabrielli S, Akinci A, Ventura G, Napolitano F, Del Pezzo E, De Siena L (2022) Fast Changes in Seismic Attenuation of the Upper Crust due to Fracturing and Fluid Migration: The 2016–2017 Central Italy Seismic Sequence, Front in Earth Sc. 2022, 10: 909698 Fehler M, Roberts P, Fairbanks T (1988) A temporal change in coda wave attenuation observed during an eruption of Mount St. Helens. J Geophys Res 93: 4367–4373 Giampicolo E, D’Amico S, Patanè D, Gresta S (2007) Attenuation and Source Parameters of Shallow Microearthquakes at Mt Etna Volcano, Italy. Bull Seismol Soc Am. 97: 184-197 Grêt A, Snieder R, Aster RC, Kyle PR (2010) Monitoring rapid temporal change in a volcano with coda wave interferometry. Geophys Res Lett 32: L06304, doi:10.1029/2004GL021143 Guardo R, De Siena L, Prudencio J, Ventura G (2022) Imaging the absorbing feeding and eruptive pathways of Deception Island, Antarctica. Geoph Res Lett, 49, e2022GL099540. https://doi. org/10.1029/2022GL099540 Guo Z, Wang X, Jiao J, Chen H (2021) Rock Physics Model and Seismic Dispersion and attenuation in Gas Hydrate-Bearing Sediments. Front Earth Sci 9:641606. https://doi.org /10.3389/feart.2021.641606 Gusev A, Lemzikob VK (1985) Properties of scattered elastic waves in the lithosphere of Kamchatka: parameters and temporal variation. Tectonophysics 112: 137-153 Iyer HM, Dawson PB (1993) Imaging volcanoes using teleseismic tomography. In: Seismic tomography, theory and practice. pp 466-492 Jin A, Aki K (1986) Temporal change in coda Q before the Tangsham earthquake of 1976 and the Haicheng earthquake of 1975. J Geophys Res 91: 665–673 Kvamme LB, Havskov J (1989) Q in southern Norway. Bull Seismol Soc Am 79: 1575–1588. Liu T, Bao X, Geng J, Zhu X, Li A, Tian D (2024) Estimation of Seismic Attenuation and Gas Hydrate Concentration from Surface Seismic Data at Hydrate Ridge, Cascadia Margin. J Geophys Res 129: e2023JB027123. https://doi.org /10.1029/2023JB027123 Londono JM (1994) Temporal change in coda Q at Nevado Del Ruiz Volcano, Colombia. J. Volc Geoth Res 73:129-139. https://doi.org/10.1016/0377-0273(95)00084-4 Londoño JM, Sudo Y (2002) A warning model based on temporal changes of coda Q for volcanic activity at Nevado Del Ruiz Volcano, Colombia. Bull Volcanol 64: 303–315 https://doi.org /10.1007/s00445-002-0207-4 Londono JM, Galvis BE (2018) Seismic Data, Photographic Images and Physical Modeling of Volcanic Plumes as a Tool for Monitoring the Activity of Nevado del Ruiz Volcano, Colombia. Front in Earth Sc 6:162. https://doi.org /10.3389/feart.2018.00162 Lundgren P, Samsonov SV, López CM, Ordoñez M (2015) Deep source model for Nevado del Ruiz volcano, Colombia, constrained by interferometric synthetic aperture radar observations. Geophys Res Lett 42. http://dx.doi.org/10.1002/2015GL063858 Phillips W, Aki K (1986) Site amplification of coda waves from local earthquakes in central California. Bull Seismol Soc Am 76: 627–648 Priest JA, Best AI, Clayton CRI (2006) Attenuation of seismic waves in methane gas hydrate-bearing sand. Geophys J Int 164: 149–159. https://doi.org /10.1111/j.1365-246X.2005.02831.x Moncayo E, Vargas C, Durán J (2004) temporal Variation of Coda-Q at Galeras Volcano, Colombia. Earth Sci Res J 8: 19 – 24. Pulli JJ (1984) Attenuation of coda waves in New England, Bull. seism.Soc. Am., 4: 1149–1166. Roecker SW, Tucker B, King J, Hatzfeld D (1982) Estimates of Q in central Asia as a function of frequencyand depth using the coda of locally recorded earthquakes. Bull Seism Soc Am 72: 129–149 Snieder R, Hagerty M (2004) Monitoring change in volcanic interiors using coda wave interferometry: Application to Arenal Volcano, Costa Rica. Geophys Res Lett 31: L09608, https://doi.org /10.1029/2004GL019670 Saccorotti G, Lokmer I (2021) A review of seismic methods for monitoring and understanding active volcanoes. Forecasting and Planning for Volcanic Hazards, Risks, and Disasters, pp. 25–73 Sato H (1977) Energy propagation including scattering effects. Single isotropic approximation. J Phys Earth 25: 27-41 Singh S, Herrmann RB (1983) Regionalization of crustal coda Q in the continental United States. J Geophys Res 88: 527–538 Tisato N, Madonna C, Saenger EH (2021) Attenuation of Seismic Waves in Partially Saturated Berea Sandstone as a Function of Frequency and Confining Pressure. Front Earth Sci 641177. https://doi.org /10.3389/feart.2021.641177 Titzschkau T, Savage M, Hurst T (2010) Changes in attenuation related to eruptions of Mt. Ruapehu Volcano, New Zealand, J Volc Geoth Res 190: 168-178.10.1016/j.jvolgeores.2009.07.012 Tusa G, Malone SD, Giampiccolo E, Gresta S, Musumeci C (2004) Attenuation of short-period P-waves at Mount St. Helens. Bull Seis Soc Amer 94: 1441-1455 Zarifi Z, Havskov J, Hanyga A (2007) An insight into the Bucaramanga nest. Tectonophysics 443: 93–105. https://doi.org/10.1016/j.tecto.2007.06.004 Cite Share Download PDF Status: Posted Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7530112","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":515001727,"identity":"187645cb-9f37-4ab3-83d0-228f4a8b8bd7","order_by":0,"name":"John Makario Londono","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1UlEQVRIiWNgGAWjYBACxgYGZiAlwcBPuhbJBhIsYgaTBgeIVj/t8GODn3ss5IzPH7/4geGXTWID+2H8uhlnpxkn9jyTMDa7kVMswdiXltjAk5ZAQEuC8QGeAxKJ227wpDEw9hw2ZpDgMSCgJf3zwT9ALZv7zxCtJcc4GWTLBob0YwwMPw7LEaOl2FjmgISxxI0cZonEhjQ5NkJ+MZydvlnyzYE6Of7+4w8/fPhjw8NPKMQMG+BMoHsS2xgY2PCqBwJ5BJP9AQPDH0LqR8EoGAWjYCQCAP3AQ1d2SC9yAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-1805-6048","institution":"Universidad Catolica de Manizales","correspondingAuthor":true,"prefix":"","firstName":"John","middleName":"Makario","lastName":"Londono","suffix":""},{"id":515001728,"identity":"1ac3f488-14e4-4f4d-8c9f-f8a78853db5a","order_by":1,"name":"Beatriz Elena Galvis","email":"","orcid":"","institution":"Servicio Geologico Colombiano","correspondingAuthor":false,"prefix":"","firstName":"Beatriz","middleName":"Elena","lastName":"Galvis","suffix":""}],"badges":[],"createdAt":"2025-09-03 20:27:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7530112/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7530112/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":91962336,"identity":"6c5fb133-85df-4d27-99d6-ec9c67ce9667","added_by":"auto","created_at":"2025-09-23 07:54:56","extension":"xml","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":7230,"visible":true,"origin":"","legend":"","description":"","filename":"buvoBUVOD2500158.xml","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/ee7212beef965e5bce094f32.xml"},{"id":91960374,"identity":"24a0daf6-2e43-4c52-8daa-ad61b9be518b","added_by":"auto","created_at":"2025-09-23 07:46:56","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":974,"visible":true,"origin":"","legend":"","description":"","filename":"BUVOD25001584169.go.xml","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/f2fc4be7207719c1ec41aeab.xml"},{"id":91960378,"identity":"b13fc48a-1f08-4abc-a259-5c5360c98705","added_by":"auto","created_at":"2025-09-23 07:46:56","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":963,"visible":true,"origin":"","legend":"","description":"","filename":"BUVOD2500158Import.xml","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/001d66e9f246a90ae7c5733e.xml"},{"id":91960386,"identity":"c71f8682-f32c-4f25-88a1-81ec8085434e","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"xml","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":74682,"visible":true,"origin":"","legend":"","description":"","filename":"BUVOD25001580enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/df1f442a82ec8857cc59ee8b.xml"},{"id":91960381,"identity":"4ba188d1-92ca-45ee-868f-71c48693fe78","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"jpeg","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":214995,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/6b4c32c60258bf214ae7f742.jpeg"},{"id":91962351,"identity":"d0e532e0-9908-41a9-8284-7f2f5bb22210","added_by":"auto","created_at":"2025-09-23 07:54:57","extension":"emf","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":22578652,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.emf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/8fcd035b648e120935f5a7ea.emf"},{"id":91962344,"identity":"2d615988-32c9-41d6-87bc-98c665be9141","added_by":"auto","created_at":"2025-09-23 07:54:57","extension":"emf","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2599336,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.emf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/35295ce05c8910b2e77d15e8.emf"},{"id":91960401,"identity":"28a34298-2f9f-4e3e-b6cd-13bdb38408c9","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"emf","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":9635480,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage4.emf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/6a27712623a923c709e12273.emf"},{"id":91963307,"identity":"30a34269-2db9-4bb9-8b88-01fc79a6b641","added_by":"auto","created_at":"2025-09-23 08:02:57","extension":"emf","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":622224,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage5.emf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/d50a5320908506a0d408df3b.emf"},{"id":91962340,"identity":"a1782ad1-2c30-4e6d-97f5-d0ec44f87e9a","added_by":"auto","created_at":"2025-09-23 07:54:57","extension":"emf","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":686516,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage6.emf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/a4c22c376880326d9fdf1a38.emf"},{"id":91964045,"identity":"daffca79-75b5-48c0-b626-9b134e1a13a1","added_by":"auto","created_at":"2025-09-23 08:11:33","extension":"emf","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":684288,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage7.emf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/aac51c2254c5af8d0725ed41.emf"},{"id":91963308,"identity":"d3eb86ef-d413-450c-b233-517a5cf5a9f1","added_by":"auto","created_at":"2025-09-23 08:02:57","extension":"emf","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":669428,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage8.emf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/540ede4fe0be7a3ffd835b92.emf"},{"id":91960393,"identity":"9406c0f5-e170-4a2f-b7e3-3ca96c2f4218","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"emf","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":685236,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage9.emf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/0242a0293e4de36629038bf5.emf"},{"id":91962341,"identity":"c20059b3-4377-4d92-b80b-9bac60b5b569","added_by":"auto","created_at":"2025-09-23 07:54:57","extension":"wmf","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1296,"visible":true,"origin":"","legend":"","description":"","filename":"image1.wmf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/82faf784046a3285a2b1f5e9.wmf"},{"id":91960387,"identity":"55d31b7b-088a-4a06-8ae1-ae8e733826ca","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"wmf","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":588,"visible":true,"origin":"","legend":"","description":"","filename":"image2.wmf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/fedee63a101f295b237bcaa0.wmf"},{"id":91960388,"identity":"2d50b7cc-6ef9-456b-8efd-bb38f465791d","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"wmf","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1180,"visible":true,"origin":"","legend":"","description":"","filename":"image3.wmf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/d5553128d466d93fa349a2e4.wmf"},{"id":91960389,"identity":"9b8cd0c8-b829-4098-8f88-cd4cf61593e9","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":31938,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/97e0f87dc3e2783a76f1a069.png"},{"id":91960407,"identity":"0958a588-f3bb-47b1-9f0a-650a18178a22","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":3794035,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/ee13a96dec78b6bcf159c1da.png"},{"id":91962345,"identity":"22ab2771-18c6-4248-8ce3-6deb84862f90","added_by":"auto","created_at":"2025-09-23 07:54:57","extension":"png","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":184126,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/d27bfc649968b6cfe7d0c5c9.png"},{"id":91960399,"identity":"2c738571-626a-4b20-a8b9-a03747d08be2","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1814303,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/46974189ad6f664f1195a6c7.png"},{"id":91962347,"identity":"f1483aa8-9ec1-4a2a-ba03-2d38b32147ac","added_by":"auto","created_at":"2025-09-23 07:54:57","extension":"png","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":594454,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/33b2eacc181f7999be3dfb39.png"},{"id":91960405,"identity":"3d35fc09-1368-4871-be9d-014eeb41e2fa","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":736153,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/62ae2638042154d13b174868.png"},{"id":91963310,"identity":"aa1d6857-e241-410b-8856-873ebc6cb34c","added_by":"auto","created_at":"2025-09-23 08:02:57","extension":"png","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":825646,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/72978f703b5f3ae2c9a091b8.png"},{"id":91960411,"identity":"2c81ff1f-67a0-4423-9d7f-7c232ceb6f2d","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":807241,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/12f37f86ca892be9a22c2ce3.png"},{"id":91960409,"identity":"8becb52b-1262-4e96-afa6-03ae36f2ba9d","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":656207,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/f1537ed8516606ed6a15237d.png"},{"id":91960398,"identity":"90651c0b-aa90-4fb6-8b97-1351594bf518","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":26,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1881,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/409bc4428cec02bf4c113f3c.png"},{"id":91960397,"identity":"2bf360c8-895e-4d5d-a69b-00bef9ff7ca7","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":27,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":528,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/0d62b6d59559094994c85202.png"},{"id":91963309,"identity":"e1c52303-00fc-4fc1-85bb-1ff00afaae6b","added_by":"auto","created_at":"2025-09-23 08:02:57","extension":"png","order_by":28,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1205,"visible":true,"origin":"","legend":"","description":"","filename":"Onlineimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/d3e14acb20278ab532a4b65a.png"},{"id":91962349,"identity":"86e74c34-6d93-48da-b48e-5ca6b1f4be65","added_by":"auto","created_at":"2025-09-23 07:54:57","extension":"xml","order_by":29,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":74412,"visible":true,"origin":"","legend":"","description":"","filename":"BUVOD25001580structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/5491a78943d8391b776eb397.xml"},{"id":91960403,"identity":"df330134-1240-42f4-b4a8-12c62833f319","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"html","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":79841,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/e63d545a38c7ca58d9a7f9ef.html"},{"id":91960372,"identity":"75fa7c82-823f-42c3-ae7e-e7b9bf3d48a0","added_by":"auto","created_at":"2025-09-23 07:46:56","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":111938,"visible":true,"origin":"","legend":"\u003cp\u003eSketch of the seismic wave attenuation configuration occurring from a distance intermediate-depth seismic nest to a local seismic network deployed on a volcanic region\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/dbc06b0a8b8995694e2009c3.png"},{"id":91960375,"identity":"bbf32369-9396-45c9-9695-7ab92c9fa603","added_by":"auto","created_at":"2025-09-23 07:46:56","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1528643,"visible":true,"origin":"","legend":"\u003cp\u003eLocation map of the study zone. a) earthquakes used for analysis (red circles). b) cross section with hypocenters (color circles). Grey triangle represents seismic station (image from Google Earth ®)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/cc1371478fe34a4e5abd267c.png"},{"id":91960373,"identity":"4e009ad5-7952-48a8-9070-149c2fac4051","added_by":"auto","created_at":"2025-09-23 07:46:56","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":821906,"visible":true,"origin":"","legend":"\u003cp\u003eLocation of NRV and seismic station used for analysis (black triangles)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/227c644b8930b39e147ef53e.png"},{"id":91963305,"identity":"bc05734a-c7ee-4dbc-85b6-80c8acde223e","added_by":"auto","created_at":"2025-09-23 08:02:57","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1209822,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of several seismic traces of BSN at BIS1 station located at NRV. a) unfiltered traces with their corresponding correlogram and spectra. b) filtered traces (8-16 Hz) with their corresponding correlogram and spectra\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/7b9ff2f6fbd0ad9dbe2710d1.png"},{"id":91960383,"identity":"94592057-661f-4446-83cf-96bebd144597","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":199890,"visible":true,"origin":"","legend":"\u003cp\u003eTemporal variation of seismic attenuation at BIS1 seismic station from earthquakes coming from BSN. The blue circles correspond to the average monthly attenuation value, and the dotted gray line represents the standard deviation\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/fc473614e65aa0a7bba70c3f.png"},{"id":91962337,"identity":"7499980e-41f5-47d0-95e0-8475f99fdb39","added_by":"auto","created_at":"2025-09-23 07:54:57","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":274939,"visible":true,"origin":"","legend":"\u003cp\u003eTime series of seismic attenuation (red dotted line and red circles) compared to monthly SO\u003csub\u003e2\u003c/sub\u003e flux (green line and boxes). Gray dotted lines correspond to the standard deviation of seismic attenuation\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/f84ebf8b6e5b753c29607a02.png"},{"id":91960379,"identity":"b18887a1-1826-4b81-8141-62458b6ffc3b","added_by":"auto","created_at":"2025-09-23 07:46:56","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":287710,"visible":true,"origin":"","legend":"\u003cp\u003eTime series of the monthly seismic wave attenuation (red dotted line and red circles) compared to radiated seismic energy (RSE) of fluid seismicity (purple line), including LP-type earthquakes and volcanic tremor. Gray dotted lines correspond to the standard deviation of seismic attenuation\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/56834ec6d2ca8e3dede72f3a.png"},{"id":91960384,"identity":"bfbb9cea-627a-45b5-b099-2c6e072960bc","added_by":"auto","created_at":"2025-09-23 07:46:57","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":267765,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of time series of monthly seismic wave attenuation with monthly duration of volcanic tremor (hours)\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/be1c2a799aea24525a432c4a.png"},{"id":91964037,"identity":"17cde553-3169-45b3-a331-0b48d007985a","added_by":"auto","created_at":"2025-09-23 08:11:32","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":260087,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of time series of monthly seismic wave attenuation with the monthly ratio RSE/SO\u003csub\u003e2\u003c/sub\u003e. The RSE/SO\u003csub\u003e2\u003c/sub\u003e ratio was normalized\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/f2aab37080c8dbf2b7470b96.png"},{"id":93160286,"identity":"59785ba7-e62d-465d-9780-e020b81cb33d","added_by":"auto","created_at":"2025-10-09 16:32:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5499411,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7530112/v1/ac5b5c5c-8fea-4258-b2bc-fa78c4df772c.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eTracking the temporal evolution of seismic attenuation at a volcano by using remote seismicity occurring in a seismic nest. Case: Nevado del Ruiz volcano and Bucaramanga seismic nest, Colombia\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eOne of the important tasks in disaster risk management (DRM) is risk awareness, that is, understanding the hazards to which the community is exposed, and gaining a deeper understanding of the phenomena that generate them. By knowing these hazards better, more prevention strategies can be defined, thus reducing the effects of these phenomena on the community.\u003c/p\u003e\u003cp\u003eIn the case of volcanic eruptions, it is necessary to generate early warning systems that allow authorities to prepare to deal with any potential emergency.\u003c/p\u003e\u003cp\u003eFor this reason, it is imperative to have not only robust monitoring systems, but also techniques that allow detecting changes in some parameters of volcanic activity before an impending eruption.\u003c/p\u003e\u003cp\u003eVolcanic eruptions are one of the natural phenomena that can have the greatest impact on humanity both locally and globally. Recent large volcanic eruptions have globally affected the climate of planet Earth (e.g., Pinatubo Volcano 1991; Hunga Tonga-Hunga 2022). For this reason, it is important to be able to understand the behavior of potentially dangerous volcanoes to be better prepared for an eventual eruption.\u003c/p\u003e\u003cp\u003eVolcanic monitoring is a fundamental task to reduce the risk of disasters due to volcanic eruption. Many techniques have been used for volcano monitoring in the last decades. The more monitoring techniques are applied to an active volcano, the greater the probability of providing a better diagnosis of its activity. For this reason, the use of new methodologies or techniques becomes a critical issue to advance in better diagnoses of volcanic activity, which contributes to better preparation of the community in general to face the effects of this type of natural phenomenon. Regarding seismicity produced by volcanic activity, it should be mentioned that it is the main manifestation of the reactivation of a volcano, since it is normally associated with the movement of magma inside the volcano. One of the most common techniques used to tracking the volcano seismicity, includes counting number of earthquakes, volcanic earthquakes classification, calculating seismic energy released, spectral content of seismic waveforms, among other parameters (Saccorotti and Lokmer, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The recording of this seismicity allows to know important aspects of the internal structure of the volcano, as well as changes in the medium through which seismic waves travel. That is why recording seismic activity is essential for monitoring a volcano. However, sometimes the amount of seismicity necessary to make an appropriate assessment of volcanic activity is not recorded.\u003c/p\u003e\u003cp\u003eThe attenuation of seismic waves is a physical parameter that has been used previously to monitor changes in volcanic activity (Londo\u0026ntilde;o and Sudo \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Moncayo et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Snieder and Hagerty \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Gr\u0026ecirc;t et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Titzschkau et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) or to study its spatial distribution (Pulli \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Iyer and Dawson ). To monitor the temporal variations in seismic wave attenuation, seismicity must be generated at different locations beneath the volcano or at remote sites if tomographic 3D or 4D attenuation studies were performed (Iyer and Dawson \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Gabrielli et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Guardo et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), or at specific sites close to the volcano if the intention were to generate time series. In the latter case, unfortunately, earthquakes are not always generated with the ideal regularity or frequency to monitor the changes in quasi-real time. Typically, a retrospective analysis of seismic activity is performed, and techniques are applied to calculate the attenuation of seismic waves a posteriori. To date, there are very few techniques or methodologies that allow monitoring changes in seismic wave attenuation in quasi-real time for volcanic monitoring because of the reasons mentioned previously.\u003c/p\u003e\u003cp\u003eThis project seeks to make up for the lack of seismicity located in volcanic areas needed for their monitoring, taking advantage of the natural repetitive seismicity that occurs in a remote seismic nest (Zarifi et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). With this type of natural and repetitive seismicity, it is possible to monitor distant volcanic areas. It is possible to monitor changes in the attenuation suffered by seismic waves inside the volcano, which in turn allows us to better understand the behavior of the volcano.\u003c/p\u003e\u003cp\u003eTaking advantage of the permanent natural seismicity generated in the so-called seismic nest of Bucaramanga (Colombia) (BSN), one of the only three places in the world where permanent seismicity occurs in the same spatial location (Zarifi et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), it is proposed to use such a seismicity to detect quasi-real variations in the attenuation of seismic waves at seismic stations located on the Nevado del Ruiz Volcano (VNR), the most active volcano in Colombia to date (September 2025), which is in an eruptive period, characterized by minor eruptions with frequent ash emissions, affecting municipalities near the volcano, mainly located in the Department of Caldas, Tolima and Risaralda, center of Colombia.\u003c/p\u003e"},{"header":"2. Methods and data","content":"\u003cp\u003eThe attenuation of seismic waves can be defined in a straightforward way, as the loss of energy suffered by seismic waves when traveling through a medium or as their travel time passes. This loss of energy is reflected in a gradual decrease in the amplitude of seismic waves. Physically, the attenuation of a wave is said to be the loss of energy for each cycle. There is a portion of the seismic signal that is characterized by reflecting the effects of the path through which the seismic rays traveled, that is, the medium they passed through. This portion is called \u0026ldquo;coda waves\u0026rdquo; (Aki and Chouet \u003cspan class=\"CitationRef\"\u003e1975\u003c/span\u003e). In this way, the analysis of this portion of the seismogram (or seismic signal) allows us to extract valuable information about the medium through which the seismic waves traveled, such as how heterogeneous it is, how attenuative it is, what type of composition it may have, what level of stress it may have, among other parameters.\u003c/p\u003e\n\u003cp\u003eThe attenuation of seismic waves is the inverse of the medium quality factor, Q (therefore, the attenuation is Q\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), which is a measure of how firm or consolidated the medium is; the more compact, rigid and homogeneous the medium is, the higher the value of Q, and vice versa. In the seismic field, the quality factor Q, measured in the coda portion of the waves, is called \u0026ldquo;coda Q.\u0026rdquo; The attenuation of seismic waves can be caused by four main factors: 1) intrinsic absorption of the medium, which has to do with the properties of the medium through which the waves travel, in particular due to the loss of energy that is converted into heat and absorbed by the medium; 2) geometric expansion, which has to do with the decrease in amplitude with distance due to the advance of seismic wave fronts; 3) anelasticity of the medium; and 4) dispersion phenomena or \u0026ldquo;scattering\u0026rdquo; of the waves due to the heterogeneities of the medium.\u003c/p\u003e\n\u003cp\u003eDifferent models and methods have been developed to extract information from Q coda of earthquakes. Some of the most widely used methods due to their simplicity and ease of calculation are the Aki and Chouet method (1974) and the Sato\u0026rsquo;s method (1977). Both methods are based on the premise that coda waves are backscattered S waves in the medium, and that there is only one scatterer or heterogeneity in the medium between the seismic source and the receiver or seismic station. These models are called \u0026ldquo;single scattering\u0026rdquo; models. The difference between the two is that the Aki and Chouet (1974) method considers the seismic source and the receiver located at the same site in space, while the Sato\u0026rsquo;s method (1977) extended the Aki and Chouet (\u003cspan class=\"CitationRef\"\u003e1975\u003c/span\u003e) method and considers the scatterers distributed isotropically and considers the source-receiver distance.\u003c/p\u003e\n\u003cp\u003eA generalized, functional and linearized way of expressing seismic attenuation using the Sato\u0026rsquo;s method (1977) is as follows:\u003c/p\u003e\n\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\n \u003cdiv class=\"EquationNumber\"\u003e\u003cimg src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAtYAAADgCAYAAAAnrCFfAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAClZSURBVHhe7d19jFTV/cfxg0mj8WEND38otg24irERERRjUxV8QJ4tNvIgKQ8GAkLTCIiKiAUBBQQVq2BA+UMhCEgN4ckHUBGoWhAQSDUooNGCpgFRsalNmt/++jncs87uzsOdmTN37p15v5Kb2Tl7d2b23Nmd7z33e76nWd3/GAAAAABFOS24BQAAAFAEAmsAAADAAwJrAAAAwAMCawAAAMADAmsAAADAAwJrAAAAwAMCawAAAMADAmsAAADAAwJrAAAAwAMCawAAAMADAmsAAADAAwJrAAAAwAMCawAAAMADAmsAAADAAwJrAAAAwAMCawAAAMADAmsAAADAAwJrAAAAwAMCawAAAMADAmsAAADAAwJrAAAAwAMCawAAAMADAmsAAADAAwJrAAAAwAMCawAAAMADAmsAAADAAwJrADl99dVXpra21jRr1qzJ1qpVK7Nnz55gTyA/jz/+eNr3lbZhw4YFewFAMhBYAwilZcuWZvfu3aaurq7BduzYMdOxY8dgLyA/99xzT5P3lLZ58+YFewBAchBYA0CZ/fDDD+bmm2+2o7RcAQCA5CKwBoAyW7FihZk7d64dqe3du7e59957bbANAEgWAmsAKLORI0fWp9OMGzfOfP/99+bkyZP2PgAgOQisASBm2rZta84555zgHgAgKQisAURm48aNZsmSJRWd5qDfbcaMGebTTz8NWvJz5MgRc/XVV5uzzz47aAEAJAWBNYBIqPrD0aNHzYgRIyo6aNTv9tBDD5l33nnHPP/880FrOCpruHbtWjN69OigBQCQJATWAEpOQXXr1q1tLnG10O/63Xff2TrNYS1evNg8/PDDjFYDQEIRWAMoKRdYKriuNm6Ufv369UFLZuqnK6+80px//vm23F6+o90AgPIjsAZQMgoQd+zYYUdhq9XEiRPN9OnTs9am1gqD2q9v3762lnW3bt1skA0ASBYCawAloUl8qsc8ZMiQsqU2aNS33IutaAR64MCBZv78+UFLUy+88EKDVQdZzRIAkonAGkBJbNmyxd527drV3kZNAbVyls8777ygpXwGDx5sPv7447IH+QCA0iKwBlASL7/8sl3spByj1W60/Pjx40FLeYUZtU6KrVu32g0A0BSBNQDvVDZOk/bKlSe8aNEi8+abb8ZqoZUbb7zRjlqrb5JKJyzLli0zF198cdACAEhFYA3Au127dtlc4XIEtUq32Lx5s+ncuXPQEg8KRhXof/3110FLsmjBm379+pnDhw+zKiQAZEBgDcC7AwcOmJ49e0aeBqIR1dmzZ5vJkyebmpoac8EFFzR5DdpHZfBUfaNVq1Z2gqNGkVetWhXsURp6HWeccYZ56623gpbkUFWXdu3a2asA2hRY51OfGwCqBYE1AK8UuL766qvmkksuCVqioxQQLQd+0UUXmc8++yxobUj7qArHSy+9ZKtvaOGa9u3bmzPPPDPYo3T69+9v9u3bF9xLjqlTp5p169bZr3WrqxHVWJccAHIhsAbg1cmTJ833339vR4ujpBQQ1czWcuBKt9Cqh5dffnnw3Z8osD333HNNly5d7P1evXqZP/7xj5Hkg6tPfvzxR3vykTSajHrhhRdSXxsAsiCwBuCdAtcoy9y5FJBJkyblTD/RqLHyhLWvoxFZVe6IgkbSdfKRJOrfI0eOmGuvvTayfgKAJCKwBuDV+++/b/bv329HZqOimtnKke7UqZPNndatSu2lS0fp06ePmTdvnnnxxRcjzxM+/fTTbYB64sSJoCUZNHHxww8/THsFAADwEwJrADkpEDx48KD5/PPPg5bsNGocRc6yaOLh2rVr7SiwW7lQecAtW7bMmI6i/OChQ4faZcTXr18ftCITN+FSJQOj8u2335o33ngj0eUJAVQfAmsAOTVv3txOCGzTpk3QEh8afR4zZkyDFBBVJcllwYIF5qabbrKLtiQx5zlKLi89yvSe3/3ud+YXv/hFcA8AkoHAGkBiKZVDVT06duwYtJySLhBUWb3UJcUViGtEO4k5z1HSiPH27dvr86uTWocbAKJAYA1UIOXEjho1yuYYpwaTlUIjzKqtvHDhQjN48OCg9RT97lrhUFVBUoPAbdu22WXO9X3RbWrAmDQ6rqrDrZzy2traglMmNm7caJ588sngXlOuwoomfbqa32HoGKm/9fhJpt9X/at+1pZv6lCu/k2KSjmeQKkRWAMVRgHXr3/9a/Pcc8/ZCXyVRoFOhw4dzLRp02x1DwXGLtjTCLYWMtm5c6f93TWJcdiwYfb7vXv3Ns8++6yZMmWKDZDUR8qzVkpIEmmUXnW49TsUunS7cs2feOIJO6Ezl+nTp9tSe42vDmSiKwI6udNxSvJiMjrpOnTokE05yrfcYD79G3dxP54K+LUolTvZ1KbXqxNo/U/USSEQBQJroMIo8NEkQ+UPVyIX6LiJivrajTgrkHHtbtNiMPr+gAED7LLiK1eutO0KSlVmLzU3O2lcGbxCVrl0wdGaNWtsv2TiAnjVCA8bVDt6XE181IJBSQ6u1c/6HfK5uhG2f5MkjsdTAbUWhRo/frw9idb/Pve3r8m2OoHWCXaU8wNQ3QisASChNBqnMnj5rnKpdAal0agqSqlPLPT4S5cutc+X1Aosrp/DlhvMp3+3bt1qt3LJ9/njdDwV3OtKVE1Njdm1a5cZNGhQg/7W/QceeICFjRApAmsASCiNHmqSZj5Bg9Ji7r77bjN27NjQo6/F0vPo+ZJagSWfcoP59K/6YtmyZWUb0S70+eNwPBVU68RFV+Z0VSDTCYyO2VVXXVVQqhRQCAJroEroA1CTqDS6qZEm5R3qEqpyEZVCgeRR9ZN886s1sqfJiFHWpBY9n0Z9tZhP0qifr7jiilABaNj+1Sh4v3797DyBcgR9xT5/McdTQbHSNgql/12zZs2yternzp2b9aqAUkC6deuW88oB4AuBNVAFFFTrg2zChAnmk08+Me+8844dWVPerCZlaYJVUi/TVysdP1U1UX61ygWmVq7QdvPNNzcZTdR9jTJGXZNa9Hx63pdffjloSQbXzyrNmHoyqlvdTxW2f1XRRpNs33zzTbspsI0yZ9nH85fzeKqPNTlZaR658v41uj5y5MjgHlB6BNZAFdBozV/+8hdbQUK6dOlievXqZb92+blJC3iqnSuDp+On4EHBX+fOne3Jk4LBzZs3NxmlUwCuut2FVhEphp5Pz6vXqdeXFK6f//nPf9qJojoZfemll2zlGZWfSz15Cdu/mjSr1UFFt5poF+VVIx/PX67jqZOZDRs22NHqqK+6AGEQWANVJN3kK43E6UMKyZKaX63gbvHixWbRokV25DHTaKkLEnXMo740rufT8+r5U+uL+6LfO3XEPtuWz+is+lmjo7oCoMlwovJ5yu1VKoRSKpx8+lcnsuWcVFfs85f6eGbijkfY1Bwgnb1799p5AmHo/2o+9dsJrAEgYRRIq+SZRgwVKI4YMcLceuutOS+La8S1EmubS7pSi5m2sKOzrp8VRI8ePTpozSxs/+pxtW+5Ficq9/MXQ/nuUo6TQ1SGFStW2PSg1L9p/d2qXSfPPXr0CFpPuf322+1VnrCBOIE1ACSMSznQiOOdd95pVq1aZQMl+OX6uXGdcNdeaK56vuX7xOeIfK7n12IqbqGVfEb300n3ulXN48UXX2zSXsyERiAMjVRrkbDXXnvNLjTmrF692r5Xtc5BY7qiq/2V/qXgOxcCawCx0PhDNmlblFR5wlVz+POf/2wD7DA58hrlC5P2k+73y2erFK6fG9cJd+2NR3zD9m8+5fscnyPy2Z5fo9mbNm2yW5jHyiXd69aEac33aNyuxZxyyedkBGjs/vvvNzNnzmzyd6rRawXOmWh/Bd0atc51VYrAGkAsNP6QTdoWJZcfq5E/BXZKCdGItYKibFwlh1z7pvv98tnScekHhY7y5uJzRNc5cOBA2jxk9b8+aMeNGxe0nBK2f5XOUKp+CCPb82tkftKkSWbt2rVBS3qlPp6Z6GRAfR9m0qQqHZVz8R3Ei94zmnzs5krkS/8LVA1oyZIlQUt6BNYAkCAuoHGVJxQIKVXBTaTT95966qm0gZ2CcI2yKo1B6QxRcukTpcrr9TmiK+q/dMuYK1hTGkO6Um9h+teV73OPG+XEPwnz/Pq9dDKhlJBMSn08M9Fr02qLumKgE4BMVD1Ev9v1118ftKDaLV++3AbGxdCJnSaKZ0NgDVQg96GnS1YadRMFCu+++6792rWJgjTtl2uUDfHg8mNT836VquCOtWavDxgwIOPErv79+0deyUH0fHpePX8SNM5D1t+GAs3hw4fbVIZMwXmu/k3tBz1e1KUHsz2/fkeVEFSb0lqUDpLpf0I5j+eCBQvshFKd4Khai46Vo9elhbC0oiT1q5HqjTfeKLpE42WXXWYOHTpkT+wyIbAGKoxGatq3b1//h3/HHXfYBSG0ytorr7xi25RCoIlCuiTet29f26aFIjSZI+oPeuTHnQil5v1qdFGXKbXQj0qQZRtB7Nq1qy1V5vJso6Ln0/Pq+ZNAI6PPPPOMHZ1S+oiuDqgW/HvvvZd1xDts/06fPt0et1yVXEol3fPrhFz/I1q3bm1XKxwyZEjGE7RyHk+9JtVpVz3rn/3sZ3axG5fmc+edd9rXFDbdB9VDAXGxampq7O3Ro0ftbVp1AJDD//6J1HXu3Llu9+7dQUtm//tgrqutra37+uuvgxY4f//73+v+F7TY23Jat25d3f8CcXtco6Dn0fPpecPSe03vuaheo09R92/UCjmeQLkp5J0zZ05wLz3t07179+BeU9u2bbP76DYTRqwBVA2lSegycVju0ng+iwMkgRY40ex2jUiWOv1Hj6/n0fPpeatBlP0btWo8nkA+CKwB5HTixAlz8OBB8/nnnwct8aAcUaW+hKHL90qVyCcY0CXnUaNGmWnTplXcpWX1h/K0lXOYmqPqkx5XKUhKMQozYTCV3mt6z+m9l0RR9G/UijmeQLnV1tbaeQE+KF0qEwJrADk1b97cXHTRRaZNmzZBS/kpoFb+a5hSXy4oXrNmTd7LIGt/5ZOqQkQlBtc6aVClC980sqnjM2HChIL6Te81vef03kuqUvZv1Io9nkC53XLLLbYGfSauPrW7TUcFABSga05LJgTWABJHH/JK0cj2D9BRULNw4UI7YTPTRCxHNW/T1b3Vzy1dutQ+TiUESal69eplxo8fH9zLLFPfZKI+mzt3rn38aha2f+OO44mkGzx4sHn99deDew099thjdrVR+eCDD4wmwqosZWO7d+82AwcODO6lR2ANIHEWLVpkq5i4Ws6ZqMLJ3XffbfNBc9XaVbCuEl2ZRrT183qc+fPn232rSa6+AYC4U8317t27p12W/L777mtS7177p1KlLZXsGzFiRNCSHoE1gERRCohKbXXu3DloyUyX/ZRTl6t2qcsd1T/ObIG6Hke1jbds2RK0VL6wfQMAcTdnzhwzZcoUs3fv3qAlvMmTJ5tZs2ZlTQMRAmsAiaGR09mzZ9t/cKonqkUsMqV3aF+NLudaclk1vlUHVyPg2hQ8Zsoh1ePo8bSkdTXIp28AIO408XbmzJnmhhtuCB1cK+VQy6C3aNHCjB49OmjNjMAaQE5xqQqiFBAtSatJbVpZMhu3+mSudJGpU6eadevW2a91q0uAmSoe6HH0eMq9q4aFdPLpG9+0UMmXX34Z3AMAPxQkv/3222bVqlVBS3arV6+2gbjm2IRBYA0gEZQCsmPHDjti4JZTdstNp+P2yTaq7WgEWpf3tBJdNnocPZ4eV49fDcL2DQAkhUauH3nkkeBedvrMCTNS7RBYA/DqmmuusaO6//d//xe0FM+lgEyaNClnkOy4pb9z0WNrX01UyTXBsVj/+c9/bGCelBJyUfYNAFQCAmsA3vke0dVkQV2269Spk1EZJN0qaL7kkkuCPQqnyXmakJht9NsXBanKDU/KJMBsfaPFeVSeSseDvGsAOIXAGoBXChoVPCqI9EG5zGvXrrU5064MkvJ9W7ZsaUd/M9H3tE8uWvxFclUO8eHAgQOhUlPiIlPfaCR706ZNdosy7xoA4o7AGoBXChq1lLOCSB/mzZtnxowZ0yAYDfPYroKHAnwFgpns27cvZ+UQx6VGhN2/MT1XFCPjvmTqGx0LpeXohAcA8BMCawDeKUVDQVmxlGLQunVr07Fjx6DllDDBsHKClRusyiAa7U5Ho+Gq8OFyiHOlr7hKI4XkHCso//HHHyMZGfchV9/omGhCo1JCAACnEFgD8E4B19GjRwsuSacgVDWUVd5Iy9CmUt7vxx9/HCqPu3///ln3U7u+r/0UIOZ6van750uvW0F5ISPd5ZCpb3RstJy87iutRekg2a4IAEA1IbAG4J1GODXSrJUP86WATaWQpk2bZlf704ipC+o0gq0FS3bu3GknL2oS47Bhw+z30unatau54oor6nOFM5k+fbo9GWg8Mt6YHkePp8fNl3720ksvzXuku9wa941G7VVjWse3W7duZsiQIYnJGQeAUmtWp5knAJDFRx99ZAPcJUuWmNtuuy1ozW79+vV25cM1a9aUNfDS67j77rttWkMxQa2Ce/XBU089Zfr06RO0hqOf/e1vf2sXuMkVvOOUhx56yI6U7969O3EnIwCqFyPWAErCjeqqVF45KQgeO3asHVktNGVBP6ef1+PkG1TL8uXL7Wg1QTUAVDYCawAloVHquXPn2lQCl8pRLioHp0olmjioXOd8aP9+/frZ9JRCysrpd1+5cqUZN25c0AIAqFQE1gBKRiO0AwcOtCXzyk1BsfK2lRoSlkaqFy9ebCZMmFDwIij63f/0pz8xWg0AVYDAGkBJuVHeOKzO16tXLzN+/PjgXm5u1F0/Vwj97prkV0j6CAAgeQisAZScgmqV36ummscKqpVXXUj6CAAgmQisAUTCLfaiyiKVXPdYv9uMGTPMXXfdZUaOHBm0AgCqAeX2AOREuThETSdiWmHzhRdeCFoAIP4YsQYAAAA8ILAGAAAAPCCwBgAAADwgsAYAAAA8ILAGEMrx48dNp06dTLNmzRpsrVq1Mnv27An2AvKjSYqN31PaJk6cGOwBAMlBVRAAAADAA0asAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADyINrLdv324GDRpkevToEbQAAAAAlSHSwPrWW281K1euDO4BAAAAlSPSwPqbb74JvgIAAAAqCznWAAAAgAcE1gAAAIAHBQfWzZo1q98ee+yxjG2asOjaUu3du9dcdNFFtl0TGlPpe2pzPzd27Fhz/Phxuy1atMj+3MaNG+0kyBYtWpjDhw/bn9Nzusd0+zh6TLWntgEAAAC+FBxYHzt2zAwcONDU1taa++67z7bV1dWZMWPGNGi79tprzeTJk+3+zsGDB837779vbzds2GAnNK5YscJ+T0HyrFmzzKOPPmofb9u2bfZ7Dz30kFmyZIl54IEHzKFDh8xf//pXM2fOHPszJ0+eNA8++KD55S9/aR9Tz3XLLbeY3r171wfdAAAAQCkVHFi3bNnSDB061Aa5GpV2mjdv3qBNo8wnTpyw+zsaTR49erT9ulevXvb2iy++sLcKnhVoKzjXCPN1111nf/7ZZ5+1wfqkSZPsfr/5zW9Mhw4d7ITIn//85zYQv+OOO+zPtGrVyu4vq1evtrfaV4G6ez4AAADAp6JyrBWkKgBevnx50HJKatumTZtMnz597Ndh7Nq1y45EKwhuvKWqqakJvjLm448/trfpfsaNnAMAAAClVPTkRaWDuDQO3fbs2dOMGjXKjhhrtHrr1q15jxK/9dZbwVf5SR05BwAAAKJUdGA9YMAAm6qhSYH79++3OdW33367/Z5Gq5Uako8LL7zQvP7663bCYmp+dOMJjqlat25tb7UATerkRAXamuwIAAAAlFrRgbVyl5X6MXXqVNO+fXvbpuC4e/fuNudZudCORrBTb8V9/d1339nbiRMn2mBcI94uz1qbqn+I2y+Vnk8TJBXga8Ki+xnlZ3fr1s3uQ1UQAAAAlFLRgbUoHURBbeqo8vDhw22AnJoGokmF8sEHH9hSeRpRdm2afKg2Bclvv/22ueqqq2y7HkOVRmbMmGHL6Wk/0eOnpn488sgjNrh2I+T6eVUc0eMBAAAApdasTjP8AAAAABTFy4g1AAAAUO0IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAEAAAAPCKwBAAAADwisAQAAAA8IrAGgzDZu3GhWrVplfvjhh6AlGnpebUlG36X31VdfmdraWtOsWbMmW6tWrcyePXuCPavL448/nrZPtOl7QLEIrAGgTBQMjho1ynz//fdmwIAB5uyzzw6+E41evXqZ888/3wwcODDywLRY9F1uF154oTl69Kipq6trsB07dsx07Ngx2Ku63HPPPU36Q9u6deuCPYDiEFgDQBkoGBsxYoQZM2aMGTRoUNAaPQVYkyZNMiNHjrSjnElA3wGIKwJrACiDqVOnmiFDhsRi5FCv4f777zfjxo1LxMg1fQcgrgisASBiyuVs3bq16dOnT9BSfgoQr776arNo0aKgJZ7oOwBxRmANwNJomyZjKUB4/vnng9ZTdJn74YcfDu4ZO/FJE6CY7JM/9eXOnTvN4MGDgxY/dPxmzJhR1Kjp6NGjzY4dO2I7sa0Ufeej3yTufVcMX33kS9xeD5CKwBqA/YDq16+f6d27tw1ctm3bFnznlOXLl9s290F23nnn2YlR+/bts/cRnvqyc+fOduKbTxotPfPMM4uaxKefVYrF/Pnzg5Z4KUXf+eg3iXvfFaOYPtLJULdu3bzmoPs6ZkApEFgDsB9QmzdvNp988okNmI8cOVIfROsDceHCheazzz4zJ0+etG0KbPThdt1119n7CEd9qlHNG2+8MWgpnh5TVxNmzZrl5XGvvPJKW0nCZyDkg+++891vEte+K1Qp+qgYcXs9QDoE1gDqKWBu27ZtgyB6w4YNdpSwsU8//dSOcCM89ZlcfPHF9rZYW7duNW3atDHTpk0zx48fN506dSo6PUfvAeUw79q1K2iJB599V4p+k7j2XSFK1UeFitvrATIhsAZQTyPXF1xwQXDv1Gh1TU2NDay/++478/XXX9e3i89L8tXgrbfesjnsvi5hX3/99Wb//v32KsO8efNsPV7V6S1W//79zcsvvxzciweffVeqfpM49l0hStlHhYjb6wEyIbAG0MDll19eH0QfPHjQLoRxySWX2FEipYiI8q3VjvwoJ1196ZNGR3W8fF4a18nVjz/+aC+9x4XvvitFv0kc+65QpeqjQsXt9QDpEFgDSEuj0pqk2HiEUJfkVV7M16hrtVCgdfrpp9s8XJ80OnrFFVd4Sy8RHfdvvvmmPh2o3ErRd6XoN4lb3xWjkD4aNmyYSV0mXKkxmr+h29R27ZevbK9HlYxUqUiPTYoIyonAGkADblRQS0W7DzCNwrVs2dKOGGkk23cwUg0UaCl33Sed/Gzfvt307NnT64nOOeecY1q0aFGf+lNuvvuuVP0mceu7QhXaRy+88IJN03CbJnPefPPNTZZW1375yPZ6dOK1adMmu+mxSRFBORFYAzGjDwl9ELmRnfXr1wffic65555runTpEtz7iYJtKoEURhVXvvzyS3Paaf7+7Zbq0rgCly+++MLs3r07aCkv331XypSCuPVdoZKUBqI+19Ly2gcoNwJrIGb0IaFLp+vWrbMTdXynDoQxduzYBhMTdXlb6R8TJ04MWpAvpQf897//De75Uap0hrjx3XfV0m/FiFsf5Xo9+v+k/1PlGIgAUhFYAzGkUWstNHHttddGXnlDS0U3vpSq16DLrFQBOUUf3u6Kgq4u6HhFLfXS+JYtW0oSUGiEsNJE0W8Spu80X2HUqFG22oleV1xE1UdhZXs9+tu799577T5KWVu6dGlZ/h4Bh8AaiCGXU6oKHYgfnXzoGN10001pcz6j4IIHXd1QioReE3KLS78pEOzRo4d57rnnbMWdOInbeyvb69Hf4SuvvGInR2qFR61+WY6/R8AhsAZiKG75jWhKo40ffvih9/J5YemS+KFDh8yrr75K6cM8xKXfdPVHr2Po0KFBS3z47CMfV7uyvR7Xj5q0eOzYMU4wUXYE1kAMuXxC0WVipRzods+ePbYN5acFSzTJsxw58ACAwu3du9fOJQpj0aJFZuPGjcG93AisgZhx+YSqgqB8QgVwqjBw+PBhm0tI/mD56Rho9KwcOfAAgMKtWLHCjBw50owePTpoMebBBx+0ZTI1iKWVhlMD6dtvv91MnTo1dCBOYA3EjOrfKg3kmmuuMePHj7f5gprx3rt3b5t6oBSExrQggptMl2tj8YTiuTQQLV/deEGMTJMZ27RpY0e3zzrrrKAl3tq1a2e3OKimvtN758knn7RXqPQ+00Riva+4YlVaukpYrrQuREcj1VOmTDGvvfaa6dChg2177LHHTPv27W31IaUV1dbW2s9bDXCJ1nDQ/jt37rRBeS4E1kDMuBSD2bNnBy0/UbtKSjWmD9/UxReybSyeULzUNJAFCxaYCRMmmCeeeMJebdAEq2qcPNX4BCPTxolddn/4wx/s+0lXqFT94uGHH66/YqVKQQAKd//995uZM2faYNnR//JBgwbZr1XiVv/Tmzdvbp555hnbJtp/5cqVdtQ612RjAmsgRjKlGKj9yJEjpm3btnZlN5RP6jHSsVCg+Pvf/95eXUh30lMtGq+4l2njxC479aMmNLoPe52kafKe5lzof0C6qyEActMI9I4dO+qDaCc1JUQUROsK0bfffhu0nKKgW+1LliwJWtIjsAZiJDXFIJUrv6c6rb5HQ9ONKua7haGcNe3rLq8llTsW+ifbr18/O2qtVB0AQHwtX77cBsZhaFT6tttuC+79RJW6Fi9eHNxLj8AaiJFMlSb0D0F51+PGjQtaGiomxzrdqGK+WzVRKURdlt+wYYNd4v3AgQPBd0or3bEsZKs26fqg0K0apPu9K2VDdXvjjTdClbDV/3flWmvSYmOXXXaZ/Z72yYTAGoiRffv2NUn30ISlWbNmmQceeCDjyGgScqxVf1bPrxSKJNMkJy0Mo5OgSy+91KaFRHF5vvFxLHQrlbjmWKfrg0K3apDu966UDdVNAXEYkydPNsuWLWuQh+3U1NTY26NHj9rbdAisgZhIXbbXpXtoBrJWE1NQTW5q+TU+RkrZUVqI0kOqHTnWAJJOn7k33HBDUQsjEVgDMaHJik8//bSdeexG9xSsvPfeewQjMdF4RUzlvOu+2pVDHqYUE+C4Scm6rKz3UGqb3lcqvSkur5+TOKB0NGiydevWJpMZ80VgDcSIzpI1a9mN7inNQBUBEA9uRUx3TFy1huHDh9t868azzYFMlOKl+txvvvmmvd+3b19bWk8TYtWmyVO6WqUTNqVPKfjWpq915QRAflSfWies6ai+tT5vFy5cGLScGr3ONFjSunXr4KumCKwBRELLwmoUXrdJpSsIqXWqdav7x44dyxlUf/7553ZU8l//+lfQEm+ffPKJ3eKgEvtO8yX0vklNk9Hqbno/ufv6vk62lRvq2vR1mNU+T5w4YT766CN7i9z+/e9/m7fffju4h0p0yy231F8ZSqWTV6V/PProo/VXi7XdcccdTaqIvPvuuzZAV1WoTAisAUTiiy++sLd33XWXvQUAICqDBw82r7/+enDvFAXVWmUx3QnoVVdd1SSA1mJNAwcODO6lR2ANICPle+pSmJb6dWfxrVq1sksu51sJ45FHHrEjbnPmzAlaAACIhtKounfv3iC9w1WrSrdpCfNUSsVSyb4RI0YELekRWANIS/98lAOqsnJaWtn9s9EyrwqSlQuab3CtvFHV6QYAIGoa2JkyZYrNqc6XyvCp9G22NBAhsAbQhGoNK79MQbRWmUqdQKlcYpX/0wSrfPKldcntb3/7W9EzrpNKJyla+Oess84KWoqnE5sZM2bkfYITRrt27ewWB777rpT9JnHqOx9K3V/5itvrQXJ06NDBzJw50+ZUhw2uNSCkz70WLVqE+vwisAbQgILqiRMnmnnz5mWckKdycyqen8/iKLrkVkxtUDSlE5szzzzT+zL3opQflROsRKXsN6m0vit1f+Urbq8HyaLPNU1UXbVqVdCS3erVq20gnloxJBsCawD13CqPWlkw25n5eeedZ1M6qKsbnuszH3Qyo9JsOlZhluhNOl99V239Vqy49RfHD75o5FopjWHoszCfK60E1gAsfWjde++99rLXuHHjso4GaeGKTPVAkZmPExEtYKDUiGnTptlj1alTJ+/LhOu98I9//CO4Fw/F9l0U/SZx7LtCRNVfYcXt9QCZEFgDsD799FPz4Ycf2tHqrl27Bq3paWU4fbhplnWYmrow5pxzzjFt27YN7hXu+uuvN/v377cTaJSuowmlvlfmVAD7zTff2JHiOPDRd1H0m8St7woVVX+FFbfXA2RCYA3AUvUPBcs9e/bMmbuoFQjl8ssvt7fITX2qANEtU10MLXKQurS6b3qNmqij1xsHvvqu1P0mceu7YkTRX/mI2+sB0iGwBmDt27fP3qpmdTbKw96wYYMdOVLBfYSnZXB1AlOsxkurp3r++eft5DnVHC/0UrmuSJxxxhmxmhzmo++y9ZtUat8VKld/pTNs2DDbf7m2Qvq31O97wAcCawA2L1QBgSp95KpmMH/+fDuyPXbsWNJA8qSRtqNHjwb3CvPVV1+Z7du3p72yoOO4adMmuxVzqVwBTP/+/YN78VBs32XrN6m0vmvevLn51a9+ZW8Lkau/MtGy/+q/XFu+/Vvq9/3QoUPtyRtQLAJrAPaDSgG1AmYF2JlooZgXX3wxZ9UQpKeRNuXgKkgoVLbL4TqOkyZNsvsUSq9NAazqRsdJsX2XK42gkvuuEHFLuyj1+x7whcAagOVG2TTilo5WYhw+fLgNqtesWdNk1Ai5qc+UarN8+fKgJX+5Ls937NjRTpzTSVAhFJxo5C5uVyOK7btc/SaV2neFCNNfUSr1+x7whcAagNWnTx97OVQj0qoVq8uroslYurSqlRiVP0lQXRzlpb/22msFjbzqZ9zl8C1btjQIInS8VC5R++jqw9KlS+uPYVjaXz+ncotxVGjfZes3qYa+y0eu/opattfj49gBPhFYA6i3YMECM2HCBPP000/bqgaaCNSlSxf7PX1waVIQQXVxNJrZo0cPWzIsXy5g2Lx5sznttNPsyZCjNIlXXnnFjph269bNDBkyJO9jpRXtrr76ajv6F0eF9l22fpNq6Lt85OqvqJX6fQ/41KxOmf4AENCH2NSpU03nzp0zLmmO4ukqgJbJLXfQ4qjay+zZs82SJUtiH5jQd7npRNhdgWKScW4aBT9w4EBBEx+BVIxYA6inoFppIHfddVfWoFqroCmYQOHUz7psHYd+1GuYM2eOrfiShNE++g5AXBFYA7C08qJm3Osye7t27WxN2FGjRpmNGzfWX4oV3ZdKuORdTgrCNMK5bNkyOzG0XBQYarRVdYCTMrJJ3wGIKwJrADZwVk71jh07bM6iRqTvvPNO884775jevXvb76kigy6TdurUyS4vjOIpQFTeek1NjVm1alWDE5go6CRJKQMrV65M3GgrfZfb4cOHbe5x6sIs2nTSHIfR/nLQe6Zxf2jr27dvsAdQHHKsAQAAAA8YsQYAAACKZsz/A21qw3WNkW4pAAAAAElFTkSuQmCC\"\u003e\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003e\u003cem\u003eAs\u003c/em\u003e is the maximum amplitude of the S waves, \u003cem\u003eA\u003c/em\u003e(\u003cem\u003et\u003c/em\u003e) is the average amplitude taken at time \u003cem\u003et\u003c/em\u003e and measured from the origin of the earthquake, \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e is the travel time of the S wave, \u003cem\u003ew\u003c/em\u003e is the angular frequency, \u003cem\u003eC\u003c/em\u003e is a constant and Q is the quality factor. From the slope \u003cem\u003eb\u003c/em\u003e it is possible to calculate Q by adjusting Eq. (\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e) using least squares techniques.\u003c/p\u003e\n\u003cp\u003eThis method for calculating Q have been applied in a large number of regions around the world and in different geological and tectonic environments (Roecker et al. \u003cspan class=\"CitationRef\"\u003e1982\u003c/span\u003e; Singh and Hermann 1983; Pulli 1985; Gusev and Lemzikob \u003cspan class=\"CitationRef\"\u003e1985\u003c/span\u003e; Phillips and Aki \u003cspan class=\"CitationRef\"\u003e1986\u003c/span\u003e; Ambeh and Fairhead \u003cspan class=\"CitationRef\"\u003e1989\u003c/span\u003e; Kvamme and Havskov \u003cspan class=\"CitationRef\"\u003e1989\u003c/span\u003e). Some studies suggest that the coda Q changes before the occurrence of earthquakes and volcanic eruptions, and that it could even be considered as a possible premonitory (Jin and Aki \u003cspan class=\"CitationRef\"\u003e1986\u003c/span\u003e; Fehler et al. \u003cspan class=\"CitationRef\"\u003e1988\u003c/span\u003e; Londono \u003cspan class=\"CitationRef\"\u003e1994\u003c/span\u003e; Tusa et al. \u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e; Giampicolo et al. \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e). There is no literature available on the application of a distant or remote repetitive natural source of seismicity (seismic nest) to monitor the variation of seismic wave attenuation in a volcanic area. In this study, it is assumed that the distant seismic nest (with intermediate-depth earthquakes) behaves as a point source where repetitive earthquakes are generated, and that seismic waves (S waves) travel along the same path, given the long distance between the seismic source and the seismic stations located at the volcano. If any change in seismic wave attenuation is detected with this setting of seismic source and receivers, it is due to variations in the medium close to the stations located at volcanic area. In this study it is assumed that: 1) most the medium between the source (intermediate-depth) and the receivers does not change overtime, due basically to the fact the almost all the distance traveled by the seismic waves (backscattered S-waves) is inside the upper mantle and lower crust; 2) only the portion traveled in the upper crust close to the seismic stations change due to volcanic activity; 3) no deep magma intrusions (\u0026gt;\u0026thinsp;30 km depth) or another deep phenomena who changes abruptly the medium conditions occurred during the studied period. Figure \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e shows the sketch.\u003c/p\u003e\n\u003cp\u003eFor this study, seismic traces from the Bucaramanga seismic nest (BSN here in after), recorded in the seismic station BIS1 of the local seismic monitoring network of Nevado del Ruiz (NRV) were used for the analysis. A total of 943 high-quality (high signal to noise ratio) earthquakes with magnitudes\u0026thinsp;\u0026gt;\u0026thinsp;3.5 were used for the calculation of coda Q, covering the period 2017\u0026ndash;2024. Figure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows the location map and the hypocenter of earthquakes used for this study (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWith the aim of verifying the assumption that the seismic rays of earthquakes generated at the BSN and recorded at the NRV local seismic stations follow the same trajectory, an analysis was conducted using cross correlation coefficients between the waveforms of different earthquakes coming from the BSN at the same local seismic station of NRV. Figure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows an example at the BIS1 station for some earthquakes. From this Figure it is possible to observe that the frequency spectra are very similar for the same station with an average correlation coefficient of 0.748 (0,64\u0026ndash;0.87) for no filtered waveforms, while for those filtered waveforms in the frequency band used in this study (8\u0026ndash;16 Hz) the correlation coefficient decreased with an average of 0.655 (0.60\u0026ndash;0.71). This can be due to local effects of seismic attenuation as we expected, and other factors not considered in this study.\u003c/p\u003e\n\u003cp\u003eWe choose a fixed time window of 15 s after twice the S-wave travel time for coda Q calculation. Once the seismic attenuation was calculated at the centered band of 12 Hz (Londono and Sudo, 2001) for each seismic trace, those values were grouped, and the monthly average of the seismic attenuation was calculated.\u003c/p\u003e"},{"header":"3. Recent activity of Nevado del Ruiz volcano","content":"\u003cp\u003eNRV is to date (September 2025) the most active volcano in Colombia. The reactivation started in 2010 with a small ash emission and large amounts of SO\u003csub\u003e2\u003c/sub\u003e released. In 2011 a large and deep source of ground deformation was detected to the SW of the volcano (Lundgren et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Later, in May and June 2012, two phreatic eruptions (VEI\u0026thinsp;=\u0026thinsp;1\u0026ndash;2) took place. Between August and September 2015 evidence of a dome extrusion at the bottom of the active crater was detected (such as seismicity, ground deformation, SO2 degassing, and thermal anomalies). This dome still is emplaced at the bottom of the active crater, with observed surficial changes (Castano et al 2020). From 2015, frequent ash emissions occurred at NRV (Londono and Galvis \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In 2021 an increase in volcanic tremor intensity was detected, which ended with strong seismic activity, ash emissions, and thermal anomalies, that led to change the alert level in March 2023 to orange color, lasting for three months. After 2024, the activity of NRV decreased slightly compared to the previous years. To date (September 2025) NRV continues unstable with frequent minor eruptions.\u003c/p\u003e"},{"header":"4. Results","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the average monthly value of attenuation for the period analyzed January 2017-February 2024. A general oscillatory trend of attenuation over time can be observed, with increases and decreases. An increase is observed between 2017 (April) and 2018 (January). Subsequently, a decrease is observed until the beginning of 2020 (March) and then an increase in attenuation until mid-2020 (June) and from that date a general tendency to decrease is observed until mid-2022 (August). Then, a constant increase is observed until the beginning of 2023 (February) and subsequently a decrease until mid-2023 (August). The variation in attenuation ends with a slight increase from that date until the end of 2023 (October) and subsequently a decrease until early 2024 (March).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo observe the relationship of the temporal variations of seismic attenuation with the activity of the VNR, a comparison of the seismic attenuation with other parameters such as the SO\u003csub\u003e2\u003c/sub\u003e monthly flux and the radiated seismic energy (RSE) of earthquakes associated with fluid activity (LP earthquakes and volcanic tremor, Chouet and Matoza \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) was made for the analyzed period. Figures\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e show the comparisons. In Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e it can be observed that there seems to be a negative relationship with the monthly SO\u003csub\u003e2\u003c/sub\u003e flux, particularly for 2019 and 2021. While SO\u003csub\u003e2\u003c/sub\u003e flux trend seems to decrease over time, the seismic wave attenuation seems to increase at NRV during the studied period.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the case of Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, it is possible to observe that there is no clear correlation between seismic wave attenuation and RSE of seismicity associated with fluids activity before 2021 but after middle 2021 there is a positive correlation with some shifting in time. From October 2021 to April 2022 the most intense volcanic tremor occurred since the last eruption (dome extrusion) in 2015. This event was associated with an initial increase and then a decrease in seismic wave attenuation. From November 2022 to April 2024 a general tendency of increasing in seismic wave attenuation was associated with a fluctuating variation in the RSE of tremor and other seismicity related to fluid activity inside NRV.\u003c/p\u003e\u003cp\u003eFrom Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e it is possible to observe that there is no clear correlation between seismic wave attenuation and duration of volcanic tremor. Even though it is possible to observe a tendency after June 2021, like that observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, in which both parameters started to change more intensively, that is, larger values were observed in both.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"5. Analysis and interpretation","content":"\u003cp\u003eSeismic wave attenuation has changed over time at NRV. From seismic data coming from BSN it was possible to detect such temporal changes in the studied period (2017\u0026ndash;2024). Those temporal changes in seismic wave attenuation can be associated with changes in SO\u003csub\u003e2\u003c/sub\u003e flux, RSE of seismicity associated with fluid dynamics, and duration of volcanic tremor.\u003c/p\u003e\u003cp\u003eThe SO\u003csub\u003e2\u003c/sub\u003e flux has decreased over time, as we mentioned previously (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). One possibility is that the SO\u003csub\u003e2\u003c/sub\u003e is released into the atmosphere, decreasing the seismic wave attenuation beneath the NRV. On the contrary, when the release of SO\u003csub\u003e2\u003c/sub\u003e to the atmosphere decrease, it means that the gas is retained inside the volcano, increasing the seismic wave attenuation. It is well known that the presence of gas inside the media increases the seismic wave attenuation (Priest et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Tisato et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Chapman et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Guo et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Liu et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Moreover, the increasing of RSE of seismicity associated with fluid dynamics may indicate that more fluids are available beneath the volcano. As we mentioned previously, after 2021 this was the case of NRV (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), suggesting that more fluids were available in the plumbing system of NRV, yielding to increasing the seismic waves attenuation. This suggestion is supported by the fact that the duration of volcanic tremor increased after 2021, which indicates, again, that it is possible that more fluids were circulating beneath the volcano.\u003c/p\u003e\u003cp\u003eTo compare the relationship of the RSE of seismic activity related to fluids inside the volcano and the flux of SO2 to the atmosphere with the seismic wave attenuation, we plotted the monthly ratio of RSE to SO2 flux and the seismic wave attenuation (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e). We found that effectively in the middle of 2021 there is a change in this ratio that correlates with a general tendency to increase the seismic wave attenuation over time. This is remarkable because it corroborates that there was a real change inside the volcano related to more fluids circulating in the magmatic and/or hydrothermal system, which probably affected the seismic wave attenuation (increase). The frequency band used in this study (6\u0026ndash;16 Hz) was previously analyzed and defined by Londono (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1994\u003c/span\u003e) by using multiple-scattering methods as a proper band to detect changes in the fluids or temperature at NRV due to intrinsic absorption of the media, due to the coda Q values for this frequency band are very similar to those obtained for Q intrinsic (Qi), indicating that Q scattering (Qs) has less influence in this frequency band at NRV.\u003c/p\u003e\u003cp\u003eThe results of this study show the utility of the remote seismicity produced by a seismic nest to be used as an additional monitoring tool of volcanic activity providing the size of the earthquakes and the distance volcano-seismic nest are between suitable ranges to be tracked over time. In the case of BSN, there are several active volcanoes that are close enough (around 300km faraway) to allow remote seismic monitoring, such as NRV, Nevado de Santa Isabel, Cerro bravo volcano, and Cerro Mach\u0026iacute;n volcano. This is the first study that uses remote seismicity produced in a natural seismic nest to monitor a volcano seismically. We focused on seismic wave attenuation monitoring (coda Q) but other seismic parameters can be monitored as well, such as P and S wave velocity, Vp/Vs ratio, among others.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"6. Conclusions","content":"\u003cp\u003eSeismic wave attenuation changes over time were investigated at NRV by using remote seismicity located in the BSN. We could confirm that the seismic attenuation at NRV has changed over time due to the presence of fluids inside the volcano. Fluctuations of the seismic attenuation (increase and decrease) were observed during the period analyzed. After 2022 a continuous increase in the seismic wave attenuation was observed and was related to an increase in fluids inside the volcano, which had increased particularly from 2021, evidenced by the decrease of SO\u003csub\u003e2\u003c/sub\u003e releasing to the atmosphere and the increase of volcanic tremor beneath the active crater.\u003c/p\u003e\u003cp\u003eThe natural occurrence of seismicity in a seismic nest can be used as an additional volcano monitoring strategy if the volcano is close enough to record those repetitive earthquakes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgments\u003c/p\u003e\n\u003cp\u003eWe want to thanks to the colleagues of the volcano observatory of Manizales (OVSMA) of the Colombia Geological Survey (CGS) for providing the information of the seismic stations of the NRV, particularly to Carolina Acosta and C\u0026eacute;sar Vega for the seismic data format transformation. We thank the National Seismic Network of CGS for providing the seismic data set of BSN. We also thanks to the Catholic University of Manizales for supporting this research.\u003c/p\u003e\n\u003cp\u003eFunding Declaration\u003c/p\u003e\n\u003cp\u003eThis study was funded by Universidad Cat\u0026oacute;lica de Manizales and Servicio Geol\u0026oacute;gico Colombiano.\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003eData Availability\u003c/p\u003e\n\u003cp\u003eThe data used in this study belongs to SGC and can be accessed by previous official request to SGC headquarters.\u003c/p\u003e\n\u003cp\u003eCompeting interest\u003c/p\u003e\n\u003cp\u003eThe authors declare that here are no Competing Interests with this study.\u003c/p\u003e\n\u003cp\u003eAuthor contribution\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation and data collection were performed by John M Londono (JML) and Beatriz E Galvis (BEG). The first draft of the manuscript was written by JML and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAki K, Chouet B (1975) Origin of coda waves: source, attenuation and scattering effects. J Geophys Res 80: 3322\u0026ndash;3342\u003c/li\u003e\n\u003cli\u003eAmbeh WB, Fairhead JD (1989) Coda Q estimates in west Africa. Bull Seismol Soc Am 79: 1589\u0026ndash;1600\u003c/li\u003e\n\u003cli\u003eCasta\u0026ntilde;o LM, Ospina CA, Cadena OE, Galvis BE, Londono JM, Laverde CA, Kanejo T, Ichihara M (2020) Continuous monitoring of the 2015\u0026ndash;2018 Nevado del Ruiz activity, Colombia, using satellite infrared images and local infrasound records. Earth Planets Space 72: 81. https://doi.org/10.1186/s40623-020-01197-z\u003c/li\u003e\n\u003cli\u003eChapman S, Borgomano JVM, Quintal B, Benson SM, Fortin J (2021) Seismic wave attenuation and dispersion due to partial fluid saturation: Direct measurements and numerical simulations based on X-ray CT. Journal of Geophysical Research: Solid Earth, 126, e2021JB021643. https://doi.org/10.1029/2021JB021643\u003c/li\u003e\n\u003cli\u003eChouet B, Matoza R (2013) A multi-decadal view of seismic methods for detecting precursors of magma movement and eruption. J Volc Geoth Res 252: 108-175. https://doi.org /10.1016/j.jvolgeores.2012.11.013\u003c/li\u003e\n\u003cli\u003eGabrielli S, Akinci A, Ventura G, Napolitano F, Del Pezzo E, De Siena L (2022) Fast Changes in Seismic Attenuation of the Upper Crust due to Fracturing and Fluid Migration: The 2016\u0026ndash;2017 Central Italy Seismic Sequence, Front in Earth Sc. 2022, 10: 909698\u003c/li\u003e\n\u003cli\u003eFehler M, Roberts P, Fairbanks T (1988) A temporal change in coda wave attenuation observed during an eruption of Mount St. Helens. J Geophys Res 93: 4367\u0026ndash;4373\u003c/li\u003e\n\u003cli\u003eGiampicolo E, D\u0026rsquo;Amico S, Patan\u0026egrave; D, Gresta S (2007) Attenuation and Source Parameters of Shallow Microearthquakes at Mt Etna Volcano, Italy. Bull Seismol Soc Am. 97: 184-197\u003c/li\u003e\n\u003cli\u003eGr\u0026ecirc;t A, Snieder R, Aster RC, Kyle PR (2010) Monitoring rapid temporal change in a volcano with coda wave interferometry. Geophys Res Lett 32: L06304, doi:10.1029/2004GL021143\u003c/li\u003e\n\u003cli\u003eGuardo R, De Siena L, Prudencio J, Ventura G (2022) Imaging the absorbing feeding and eruptive pathways of Deception Island, Antarctica. Geoph Res Lett, 49, e2022GL099540. https://doi. org/10.1029/2022GL099540\u003c/li\u003e\n\u003cli\u003eGuo Z, Wang X, Jiao J, Chen H (2021) Rock Physics Model and Seismic Dispersion and attenuation in Gas Hydrate-Bearing Sediments. Front Earth Sci 9:641606. https://doi.org /10.3389/feart.2021.641606\u003c/li\u003e\n\u003cli\u003eGusev A, Lemzikob VK (1985) Properties of scattered elastic waves in the lithosphere of Kamchatka: parameters and temporal variation. Tectonophysics 112: 137-153\u003c/li\u003e\n\u003cli\u003eIyer HM, Dawson PB (1993) Imaging volcanoes using teleseismic tomography. In: Seismic tomography, theory and practice. pp 466-492\u003c/li\u003e\n\u003cli\u003eJin A, Aki K (1986) Temporal change in coda Q before the Tangsham earthquake of 1976 and the Haicheng earthquake of 1975. J Geophys Res 91: 665\u0026ndash;673\u003c/li\u003e\n\u003cli\u003eKvamme LB, Havskov J (1989) Q in southern Norway. Bull Seismol Soc Am 79: 1575\u0026ndash;1588.\u003c/li\u003e\n\u003cli\u003eLiu T, Bao X, Geng J, Zhu X, Li A, Tian D (2024) Estimation of Seismic Attenuation and Gas Hydrate Concentration from Surface Seismic Data at Hydrate Ridge, Cascadia Margin. J Geophys Res 129: e2023JB027123. https://doi.org /10.1029/2023JB027123\u003c/li\u003e\n\u003cli\u003eLondono JM (1994) Temporal change in coda Q at Nevado Del Ruiz Volcano, Colombia. J. Volc Geoth Res 73:129-139. https://doi.org/10.1016/0377-0273(95)00084-4\u003c/li\u003e\n\u003cli\u003eLondo\u0026ntilde;o JM, Sudo Y (2002) A warning model based on temporal changes of coda Q for volcanic activity at Nevado Del Ruiz Volcano, Colombia. Bull Volcanol 64: 303\u0026ndash;315 https://doi.org /10.1007/s00445-002-0207-4\u003c/li\u003e\n\u003cli\u003eLondono JM, Galvis BE (2018) Seismic Data, Photographic Images and Physical Modeling of Volcanic Plumes as a Tool for Monitoring the Activity of Nevado del Ruiz Volcano, Colombia. Front in Earth Sc 6:162. https://doi.org /10.3389/feart.2018.00162\u003c/li\u003e\n\u003cli\u003eLundgren P, Samsonov SV, L\u0026oacute;pez CM, Ordo\u0026ntilde;ez M (2015) Deep source model for Nevado del Ruiz volcano, Colombia, constrained by interferometric synthetic aperture radar observations. Geophys Res Lett 42. http://dx.doi.org/10.1002/2015GL063858\u003c/li\u003e\n\u003cli\u003ePhillips W, Aki K (1986) Site amplification of coda waves from local earthquakes in central California. Bull Seismol Soc Am 76: 627\u0026ndash;648\u003c/li\u003e\n\u003cli\u003ePriest JA, Best AI, Clayton CRI (2006) Attenuation of seismic waves in methane gas hydrate-bearing sand. Geophys J Int 164: 149\u0026ndash;159. https://doi.org /10.1111/j.1365-246X.2005.02831.x\u003c/li\u003e\n\u003cli\u003eMoncayo E, Vargas C, Dur\u0026aacute;n J (2004) temporal Variation of Coda-Q at Galeras Volcano, Colombia. Earth Sci Res J 8: 19 \u0026ndash; 24.\u003c/li\u003e\n\u003cli\u003ePulli JJ (1984) Attenuation of coda waves in New England, Bull. seism.Soc. Am., 4: 1149\u0026ndash;1166.\u003c/li\u003e\n\u003cli\u003eRoecker SW, Tucker B, King J, Hatzfeld D (1982) Estimates of Q in central Asia as a function of frequencyand depth using the coda of locally recorded earthquakes. Bull Seism Soc Am 72: 129\u0026ndash;149\u003c/li\u003e\n\u003cli\u003eSnieder R, Hagerty M (2004) Monitoring change in volcanic interiors using coda wave interferometry: Application to Arenal Volcano, Costa Rica. Geophys Res Lett 31: L09608, https://doi.org /10.1029/2004GL019670\u003c/li\u003e\n\u003cli\u003eSaccorotti G, Lokmer I (2021) A review of seismic methods for monitoring and understanding active volcanoes. Forecasting and Planning for Volcanic Hazards, Risks, and Disasters, pp. 25\u0026ndash;73\u003c/li\u003e\n\u003cli\u003eSato H (1977) Energy propagation including scattering effects. Single isotropic approximation. J Phys Earth 25: 27-41\u003c/li\u003e\n\u003cli\u003eSingh S, Herrmann RB (1983) Regionalization of crustal coda Q in the continental United States. J Geophys Res 88: 527\u0026ndash;538\u003c/li\u003e\n\u003cli\u003eTisato N, Madonna C, Saenger EH (2021) Attenuation of Seismic Waves in Partially Saturated Berea Sandstone as a Function of Frequency and Confining Pressure. Front Earth Sci 641177. https://doi.org /10.3389/feart.2021.641177\u003c/li\u003e\n\u003cli\u003eTitzschkau T, Savage M, Hurst T (2010) Changes in attenuation related to eruptions of Mt. Ruapehu Volcano, New Zealand, J Volc Geoth Res 190: 168-178.10.1016/j.jvolgeores.2009.07.012 \u003c/li\u003e\n\u003cli\u003eTusa G, Malone SD, Giampiccolo E, Gresta S, Musumeci C (2004) Attenuation of short-period P-waves at Mount St. Helens. Bull Seis Soc Amer 94: 1441-1455 \u003c/li\u003e\n\u003cli\u003eZarifi Z, Havskov J, Hanyga A (2007) An insight into the Bucaramanga nest. Tectonophysics 443: 93\u0026ndash;105. https://doi.org/10.1016/j.tecto.2007.06.004\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Nevado del Ruiz volcano, Bucaramanga seismic nest, seismic wave attenuation, coda Q, Volcanic tremor, SO2 flux","lastPublishedDoi":"10.21203/rs.3.rs-7530112/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7530112/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA seismic study was conducted on the attenuation of seismic waves in the Nevado del Ruiz Volcano (NRV) for the period January 2017-December 2024, based on remote earthquakes generated in the Bucaramanga Seismic Nest (BSN), located 320 km away at northeast of the volcano and recorded in one seismic station deployed at NRV. It was possible to observe a temporal variation in the attenuation in the NRV related to changes in its activity, due to the movement of fluids inside the volcano. An increase in attenuation was detected between 2017 and 2018 and subsequently a new, larger increase between 2022 and 2024. These changes coincide with significant variations in degassing inside the volcano detected with other instruments and techniques. A negative relationship was observed between seismic attenuation and the SO\u003csub\u003e2\u003c/sub\u003e flux to the atmosphere for some periods, while a positive relationship with the radiated seismic energy of seismicity associated with fluid dynamics inside the volcano was observed as well. This behavior may indicate circulating of fluids inside the NRV which accumulate inside the volcano generating higher seismic attenuation. Some of these fluids are subsequently released into the atmosphere such as SO\u003csub\u003e2\u003c/sub\u003e, producing a decrease in the attenuation of seismic waves at NRV. This process seems to repeat itself over time. This study suggests that seismic attenuation measured in repetitive remote earthquakes located in the NSB can be used as a new tool for volcanic seismic monitoring in Colombia.\u003c/p\u003e","manuscriptTitle":"Tracking the temporal evolution of seismic attenuation at a volcano by using remote seismicity occurring in a seismic nest. Case: Nevado del Ruiz volcano and Bucaramanga seismic nest, Colombia","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-23 07:46:52","doi":"10.21203/rs.3.rs-7530112/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2f75a9be-bb91-4014-ad2f-8c964b3d8064","owner":[],"postedDate":"September 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-09T16:24:17+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-23 07:46:52","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7530112","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7530112","identity":"rs-7530112","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}