Francisco Delgado, Pablo León-Ibáñez, Juan Carlos Báez, Sofía Parra
Volcanic eruptions are currently understood as triggered by increases in the overpressure of the magma storage regions, usually resulting in ground deformation. We assess whether observations of ground deformation can provide insights on the triggering mechanisms of sub-Plinian and Plinian eruptions, which are the most hazardous eruptions with a global impact. We process and compile InSAR and GNSS time series from 1991 to 2025 spanning four eruptions of this type in the Southern Andes: Hudson 1991, Chaitén 2008–2009, Cordón Caulle 2011–2012 and Calbuco 2015, resulting in the subduction zone with the largest erupted mass during 1980–2019. Only Cordón Caulle displays the theoretical pattern of pre-eruptive uplift due to reservoir pressurization, co-eruptive subsidence due to magma extraction, and post-eruptive uplift in response to magma inflow. For the rest of the volcanoes, we observe co- or post-eruptive ground deformation, but the data temporal resolution is low and did not sample well all the eruptions. On a global scale, InSAR and GNSS data recorded at volcanoes in subduction zones that experienced similar eruptions indicate few well-recorded eruptions. Only Okmok records a similar pattern to that of Cordon Caulle, while in other volcanoes geodetic data recorded the last episodes of pre-eruptive reservoir pressurization. This implies that most of the magma that increased the overpressure could have been emplaced in the decades or centuries prior to eruption and geodetic observations, or emplaced undetected. The longer time scales of recharge in subduction zone volcanoes compared with basaltic volcanoes in hot spots could indicate larger storage regions.
{"title":"The Triggering of Sub-Plinian and Plinian Eruptions: Insights From Three Decades of InSAR Observations in the Andean Southern Volcanic Zone (1991–2025) and a Global Compilation","authors":"Francisco Delgado, Pablo León-Ibáñez, Juan Carlos Báez, Sofía Parra","doi":"10.1029/2025JB032010","DOIUrl":"10.1029/2025JB032010","url":null,"abstract":"<p>Volcanic eruptions are currently understood as triggered by increases in the overpressure of the magma storage regions, usually resulting in ground deformation. We assess whether observations of ground deformation can provide insights on the triggering mechanisms of sub-Plinian and Plinian eruptions, which are the most hazardous eruptions with a global impact. We process and compile InSAR and GNSS time series from 1991 to 2025 spanning four eruptions of this type in the Southern Andes: Hudson 1991, Chaitén 2008–2009, Cordón Caulle 2011–2012 and Calbuco 2015, resulting in the subduction zone with the largest erupted mass during 1980–2019. Only Cordón Caulle displays the theoretical pattern of pre-eruptive uplift due to reservoir pressurization, co-eruptive subsidence due to magma extraction, and post-eruptive uplift in response to magma inflow. For the rest of the volcanoes, we observe co- or post-eruptive ground deformation, but the data temporal resolution is low and did not sample well all the eruptions. On a global scale, InSAR and GNSS data recorded at volcanoes in subduction zones that experienced similar eruptions indicate few well-recorded eruptions. Only Okmok records a similar pattern to that of Cordon Caulle, while in other volcanoes geodetic data recorded the last episodes of pre-eruptive reservoir pressurization. This implies that most of the magma that increased the overpressure could have been emplaced in the decades or centuries prior to eruption and geodetic observations, or emplaced undetected. The longer time scales of recharge in subduction zone volcanoes compared with basaltic volcanoes in hot spots could indicate larger storage regions.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 12","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145777969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Brenton W. Hirao, Amanda M. Thomas, David R. Shelly, Weston A. Thelen, Cyril Journeau
Seismicity during non-eruptive periods is useful for observing stress changes related to magmatic transport and volatile exsolution within active volcanoes. Mount St. Helens in Washington, USA, is the most active volcano in the continental United States and has been in quiescence since 2008. To explore the processes driving seismicity at Mount St. Helens, we create a high-resolution seismicity catalog of non-eruptive seismicity from 2008 through 2023, consisting of 31,133 events. We find persistent shallow seismicity (−2.2 to 2 km below sea level (BSL), 0–4.2 km below the surface) throughout the entire study period that concentrates beneath the dacite dome complex from the 1980–1986 and 2004–2008 eruptions. Additionally, there is frequent deeper seismicity (2–8 km BSL, 4.2–12.2 km below the surface) beginning in 2016. We examine a selection of deep earthquake swarms and find complex along-depth seismicity patterns. Within swarms, increases in shallow seismicity rates can precede or are concurrent with increases of deep seismicity rates. Lastly, we discover a series of semi-periodic, shallow, burst-like swarms, consisting of low-amplitude, repetitive similar earthquakes, indicating periodic valve-like release of fluid pressure from the conduit. Increased seismic activity beginning in 2016 indicates ongoing repressurization within the magmatic system driven by recharge or crystallization-induced second boiling within the upper-crustal reservoir after 2008. The data indicate that non-eruptive seismicity at Mount St. Helens is controlled by fluid pressure changes from gas flux sourced from the magma reservoir that migrates through crack networks.
{"title":"Magmatic Volatile Flux Drives Non-Eruptive Volcano-Tectonic Seismicity at Mount St. Helens, USA From 2008–2024","authors":"Brenton W. Hirao, Amanda M. Thomas, David R. Shelly, Weston A. Thelen, Cyril Journeau","doi":"10.1029/2025JB031278","DOIUrl":"10.1029/2025JB031278","url":null,"abstract":"<p>Seismicity during non-eruptive periods is useful for observing stress changes related to magmatic transport and volatile exsolution within active volcanoes. Mount St. Helens in Washington, USA, is the most active volcano in the continental United States and has been in quiescence since 2008. To explore the processes driving seismicity at Mount St. Helens, we create a high-resolution seismicity catalog of non-eruptive seismicity from 2008 through 2023, consisting of 31,133 events. We find persistent shallow seismicity (−2.2 to 2 km below sea level (BSL), 0–4.2 km below the surface) throughout the entire study period that concentrates beneath the dacite dome complex from the 1980–1986 and 2004–2008 eruptions. Additionally, there is frequent deeper seismicity (2–8 km BSL, 4.2–12.2 km below the surface) beginning in 2016. We examine a selection of deep earthquake swarms and find complex along-depth seismicity patterns. Within swarms, increases in shallow seismicity rates can precede or are concurrent with increases of deep seismicity rates. Lastly, we discover a series of semi-periodic, shallow, burst-like swarms, consisting of low-amplitude, repetitive similar earthquakes, indicating periodic valve-like release of fluid pressure from the conduit. Increased seismic activity beginning in 2016 indicates ongoing repressurization within the magmatic system driven by recharge or crystallization-induced second boiling within the upper-crustal reservoir after 2008. The data indicate that non-eruptive seismicity at Mount St. Helens is controlled by fluid pressure changes from gas flux sourced from the magma reservoir that migrates through crack networks.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 12","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JB031278","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145777968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E.-J. Lee, W.-Y. Liao, I. Koulakov, P. Chen, S.-P. Chang, D.-Y. Chen, Y.-M. Wu, W.-T. Liang, Y.-T. Lo, H.-Y. Yen, Y.-H. Lee
Using dense seismic data sets, we present a new 3D velocity model of Taiwan that images a prominent mid-crustal (∼20–30 km) high-velocity body beneath west-central Taiwan. The inclusion of high-quality post-2012 recordings from the Central Weather Administration Seismic Network (CWASN) ensures the elimination of uncorrectable timing errors. In addition, a machine learning–based phase picker was applied to the entire data set to improve the consistency and accuracy of phase arrival identification. The resulting model generally aligns with previous tomographic studies. Structures inferred from velocity gradients in the tomographic profiles largely correspond to mapped faults and geological unit boundaries in Taiwan. The model also images a pronounced mid-crustal (∼20–30 km) high-velocity anomaly beneath west-central Taiwan. Under representative P–T conditions, Vp–Vs–density comparisons indicate the best match with mafic compositions, though the interpretation is not unique. This mafic interpretation is compatible with passive-margin mafic additions (underplating and/or intrusions). The anomaly coincides with reduced seismicity below ∼20 km and depth-dependent stress orientations, consistent with a relatively competent mid-crustal volume. Geological and geophysical similarities with the Dongsha Rise further suggest a possible shared tectonic and magmatic origin, likely linked to mafic underplating during South China Sea rifting. These findings improve our understanding of structural highs along passive continental margins and their role in influencing crustal deformation in the Taiwan orogen. The new model also provides a robust framework for future waveform-based seismic imaging.
利用密集的地震数据集,我们提出了一个新的台湾三维速度模型,该模型成像了台湾中西部下方一个突出的中地壳(~ 20-30公里)高速体。包括来自中央气象局地震台网(cisn)的2012年后高质量记录,确保消除不可纠正的时间误差。此外,将基于机器学习的相位选择器应用于整个数据集,以提高相位到达识别的一致性和准确性。所得到的模型通常与以前的层析成像研究相一致。从层析剖面的速度梯度推断出的构造在很大程度上与台湾的断层和地质单元边界相对应。该模型还成像了台湾中西部下方明显的中地壳(~ 20-30公里)高速异常。在具有代表性的P-T条件下,vp - vs -密度比较表明与基性成分最匹配,尽管解释不是唯一的。这种基性解释适用于无源边缘基性补充(底板和/或侵入)。该异常与~ 20 km以下地震活动性减弱和深度相关的应力方向相吻合,与相对活跃的中地壳体积相一致。与东沙隆起的地质和地球物理相似性进一步表明,东沙隆起可能具有共同的构造和岩浆成因,可能与南海裂谷期的基性底板有关。这些发现提高了我们对被动大陆边缘构造高点及其影响台湾造山带地壳变形的认识。新模型还为未来基于波形的地震成像提供了一个强大的框架。
{"title":"Tomographic Constraints on a Mid-Crustal High-Velocity Body Beneath West-Central Taiwan: Implications for Passive-Margin Mafic Additions","authors":"E.-J. Lee, W.-Y. Liao, I. Koulakov, P. Chen, S.-P. Chang, D.-Y. Chen, Y.-M. Wu, W.-T. Liang, Y.-T. Lo, H.-Y. Yen, Y.-H. Lee","doi":"10.1029/2025JB032225","DOIUrl":"10.1029/2025JB032225","url":null,"abstract":"<p>Using dense seismic data sets, we present a new 3D velocity model of Taiwan that images a prominent mid-crustal (∼20–30 km) high-velocity body beneath west-central Taiwan. The inclusion of high-quality post-2012 recordings from the Central Weather Administration Seismic Network (CWASN) ensures the elimination of uncorrectable timing errors. In addition, a machine learning–based phase picker was applied to the entire data set to improve the consistency and accuracy of phase arrival identification. The resulting model generally aligns with previous tomographic studies. Structures inferred from velocity gradients in the tomographic profiles largely correspond to mapped faults and geological unit boundaries in Taiwan. The model also images a pronounced mid-crustal (∼20–30 km) high-velocity anomaly beneath west-central Taiwan. Under representative P–T conditions, Vp–Vs–density comparisons indicate the best match with mafic compositions, though the interpretation is not unique. This mafic interpretation is compatible with passive-margin mafic additions (underplating and/or intrusions). The anomaly coincides with reduced seismicity below ∼20 km and depth-dependent stress orientations, consistent with a relatively competent mid-crustal volume. Geological and geophysical similarities with the Dongsha Rise further suggest a possible shared tectonic and magmatic origin, likely linked to mafic underplating during South China Sea rifting. These findings improve our understanding of structural highs along passive continental margins and their role in influencing crustal deformation in the Taiwan orogen. The new model also provides a robust framework for future waveform-based seismic imaging.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 12","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JB032225","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145777967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mareen Lösing, Alan Aitken, Jörg Ebbing, Jacqueline A. Halpin, Lu Li, Max Moorkamp, Anya Reading, Tobias Stål
The shared tectonic history of southwestern Australia and East Antarctica facilitates the exchange of geological insights between the regions. In this study, we present coupled susceptibility and density models obtained through the joint inversion of magnetic and gravity data. By assuming a common geological source for both signals, our coupling method minimizes misfits and variation in information, thereby enhancing a correlation between susceptibility and density. The resulting anomalies demonstrate structural continuity between the continents, aligning closely with major shear zones and seismic reflectors. Combining these results with machine learning, geochemical, and petrophysical databases, we predict a high-resolution (10 km) heat production map for East Antarctica. Utilizing a Markov Chain Monte Carlo (MCMC) algorithm, we further develop a geothermal heat flow map with greater spatial variability than previous studies, yielding an average of