Pub Date : 2026-03-01Epub Date: 2026-02-18DOI: 10.1016/j.pepi.2026.107521
Lei Guo , Jiawei Qian , Xudong Ma , Lina Sun , Yi Zhou
Since 2004, paired earthquakes with magnitudes above ML 4.0 have occurred in the Tangshan region at roughly two-year intervals. However, this regularity was disrupted in 2014. High-resolution earthquake relocation is essential for identifying the seismogenic structures responsible and understanding the underlying causes of this anomaly. In this study, we relocated 5346 earthquakes recorded by the Hebei Seismic Network between 2010 and 2022 using the triple-difference earthquake location algorithm. After relocation, the epicenters became more concentrated and exhibited a pronounced linear distribution. The dominant alignment of seismicity is northeastward, consistent with the regional fault strike. The relocated focal depths are mainly within 10–15 km, following an approximately normal distribution, indicating improved location accuracy. The spatial distribution of epicenters highlights a steeply dipping, NNE-trending seismic belt east of the Tangshan-Guye Fault, where frequent minor earthquakes suggest the presence of the steeply dipping Xujialou Fault. The ML 5.2 Tangshan earthquake in 2012 and the ML 5.4 Guye earthquake in 2020 are likely associated with this fault. The temporal pattern of local seismicity displays a sequence of clustering, quiescence, re-clustering, and stress transfer. These characteristics of moderate earthquakes in the historically active Tangshan region reflect the area's unique stress regime and complex fault architecture.
{"title":"Spatiotemporal seismicity and fault structure in Tangshan revealed by triple-difference relocation method","authors":"Lei Guo , Jiawei Qian , Xudong Ma , Lina Sun , Yi Zhou","doi":"10.1016/j.pepi.2026.107521","DOIUrl":"10.1016/j.pepi.2026.107521","url":null,"abstract":"<div><div>Since 2004, paired earthquakes with magnitudes above M<sub>L</sub> 4.0 have occurred in the Tangshan region at roughly two-year intervals. However, this regularity was disrupted in 2014. High-resolution earthquake relocation is essential for identifying the seismogenic structures responsible and understanding the underlying causes of this anomaly. In this study, we relocated 5346 earthquakes recorded by the Hebei Seismic Network between 2010 and 2022 using the triple-difference earthquake location algorithm. After relocation, the epicenters became more concentrated and exhibited a pronounced linear distribution. The dominant alignment of seismicity is northeastward, consistent with the regional fault strike. The relocated focal depths are mainly within 10–15 km, following an approximately normal distribution, indicating improved location accuracy. The spatial distribution of epicenters highlights a steeply dipping, NNE-trending seismic belt east of the Tangshan-Guye Fault, where frequent minor earthquakes suggest the presence of the steeply dipping Xujialou Fault. The M<sub>L</sub> 5.2 Tangshan earthquake in 2012 and the M<sub>L</sub> 5.4 Guye earthquake in 2020 are likely associated with this fault. The temporal pattern of local seismicity displays a sequence of clustering, quiescence, re-clustering, and stress transfer. These characteristics of moderate earthquakes in the historically active Tangshan region reflect the area's unique stress regime and complex fault architecture.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"372 ","pages":"Article 107521"},"PeriodicalIF":1.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147400823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-01-28DOI: 10.1016/j.pepi.2026.107504
S.L. Khanyile , E. Nahayo , F.J. Pavon-Carrasco , M. Puente-Borque
The Southern African region is in the eastern part of the South Atlantic Anomaly. The Earth's magnetic field variation in this region is characterized by high spatial and temporal magnetic field gradients. The study of fast core field variations requires an accurate regional geomagnetic field model that can capture temporal and spatial small-scale features of the geomagnetic field variation, which are sometimes missed by the global field models. A regional model of the Earth's magnetic field and its secular variation was developed over the Southern African region using the technique of the Revised Spherical Cap Harmonic Analysis (R-SCHA) applied on data from the Swarm satellite and ground-based magnetic measurements between 2014 and 2023. Its accuracy was validated against the global CHAOS-8.1 model and the ground-based data from four magnetic observatories in the region, Hermanus (HER), Hartebeesthoek (HBK), Tsumeb (TSU), and Keetmanshoop (KMH). The Root Mean Square Error (RMSE) for X, Y, and Z field components between the model input Swarm data and predictions from the R-SCHA model were 2.7 nT, 2.1 nT, and 1.4 nT, and from the CHAOS-8.1 model were 2.7 nT, 2.2 nT, and 1.9 nT, respectively. For ground observatory data (after removing the crustal biases), the R-SCHA model yielded RMSE values of 2.9 nT, 2.3 nT, and 1.9 nT compared to 3.8 nT, 2.9 nT, and 2.8 nT from the CHAOS-8.1 model. The R-SCHA regional model captured secular variation features consistent with ground observatory data, revealing geomagnetic jerk in 2019–2020 and a distinct V-shaped jerk in 2021 across all observatories in the X and Z components, findings that are confirmed by the CHAOS-8.1 model. The results show rapid secular variation fluctuations in the X component in 2018 at HER and TSU observatories, and an abrupt change in the linear secular variation trend around 2022–2023 at all observatories, which is clearly visible in the X and Z components. The average rate of change of the total field strength between 2018.5 and 2023.5 epochs decreases, reaching 80 nT/year in the western part of the region, while in the eastern areas it slightly increases, reaching 40 nT/year.
{"title":"Modelling earth's magnetic field over southern Africa between 2014 and 2023 applying revised spherical cap harmonic analysis (R-SCHA) on Swarm satellite and ground-based data","authors":"S.L. Khanyile , E. Nahayo , F.J. Pavon-Carrasco , M. Puente-Borque","doi":"10.1016/j.pepi.2026.107504","DOIUrl":"10.1016/j.pepi.2026.107504","url":null,"abstract":"<div><div>The Southern African region is in the eastern part of the South Atlantic Anomaly. The Earth's magnetic field variation in this region is characterized by high spatial and temporal magnetic field gradients. The study of fast core field variations requires an accurate regional geomagnetic field model that can capture temporal and spatial small-scale features of the geomagnetic field variation, which are sometimes missed by the global field models. A regional model of the Earth's magnetic field and its secular variation was developed over the Southern African region using the technique of the Revised Spherical Cap Harmonic Analysis (R-SCHA) applied on data from the <em>Swarm</em> satellite and ground-based magnetic measurements between 2014 and 2023. Its accuracy was validated against the global CHAOS-8.1 model and the ground-based data from four magnetic observatories in the region, Hermanus (HER), Hartebeesthoek (HBK), Tsumeb (TSU), and Keetmanshoop (KMH). The Root Mean Square Error (RMSE) for X, Y, and Z field components between the model input <em>Swarm</em> data and predictions from the R-SCHA model were 2.7 nT, 2.1 nT, and 1.4 nT, and from the CHAOS-8.1 model were 2.7 nT, 2.2 nT, and 1.9 nT, respectively. For ground observatory data (after removing the crustal biases), the R-SCHA model yielded RMSE values of 2.9 nT, 2.3 nT, and 1.9 nT compared to 3.8 nT, 2.9 nT, and 2.8 nT from the CHAOS-8.1 model. The R-SCHA regional model captured secular variation features consistent with ground observatory data, revealing geomagnetic jerk in 2019–2020 and a distinct V-shaped jerk in 2021 across all observatories in the X and Z components, findings that are confirmed by the CHAOS-8.1 model. The results show rapid secular variation fluctuations in the X component in 2018 at HER and TSU observatories, and an abrupt change in the linear secular variation trend around 2022–2023 at all observatories, which is clearly visible in the X and Z components. The average rate of change of the total field strength between 2018.5 and 2023.5 epochs decreases, reaching 80 nT/year in the western part of the region, while in the eastern areas it slightly increases, reaching 40 nT/year.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"372 ","pages":"Article 107504"},"PeriodicalIF":1.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-01DOI: 10.1016/j.pepi.2026.107512
Muh. Farid Wajedy , Saaduddin , Muhammad Altin Massinai , Fahruddin Fahruddin , Ahmad Thariq
Halmahera is one of the eastern regions of Indonesia that experiences intense tectonic activity due to the convergence of four major tectonic plates: the Eurasian, Australian, Pacific, and Philippine Sea Plates. Given the region's complex tectonic setting and seismic potential, this study aims to investigate the prevailing stress conditions in Halmahera using b-value and apparent stress analyses. The dataset comprises earthquake events from 1970 to 2024 with magnitudes ranging from 3.0 to 5.9 and focal depths between 10 and 50 km. The results show that the b-values in Halmahera range from 0.886 to 1.928, while the apparent stress values vary between 0.049 and 0.165 MPa. Our analysis reveals that the northwestern part of Halmahera exhibits significant stress accumulation, likely associated with ongoing subduction processes, indicating a potential for large-magnitude earthquakes. These findings highlight the importance of continuous monitoring and targeted seismic hazard mitigation efforts, particularly in the northwestern Halmahera region.
{"title":"Seismic hazard and tectonic stress in Halmahera, Indonesia based on b-value and apparent stress analyses","authors":"Muh. Farid Wajedy , Saaduddin , Muhammad Altin Massinai , Fahruddin Fahruddin , Ahmad Thariq","doi":"10.1016/j.pepi.2026.107512","DOIUrl":"10.1016/j.pepi.2026.107512","url":null,"abstract":"<div><div>Halmahera is one of the eastern regions of Indonesia that experiences intense tectonic activity due to the convergence of four major tectonic plates: the Eurasian, Australian, Pacific, and Philippine Sea Plates. Given the region's complex tectonic setting and seismic potential, this study aims to investigate the prevailing stress conditions in Halmahera using b-value and apparent stress analyses. The dataset comprises earthquake events from 1970 to 2024 with magnitudes ranging from 3.0 to 5.9 and focal depths between 10 and 50 km. The results show that the b-values in Halmahera range from 0.886 to 1.928, while the apparent stress values vary between 0.049 and 0.165 MPa. Our analysis reveals that the northwestern part of Halmahera exhibits significant stress accumulation, likely associated with ongoing subduction processes, indicating a potential for large-magnitude earthquakes. These findings highlight the importance of continuous monitoring and targeted seismic hazard mitigation efforts, particularly in the northwestern Halmahera region.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"372 ","pages":"Article 107512"},"PeriodicalIF":1.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-11DOI: 10.1016/j.pepi.2026.107516
Hao Zhang , Jianshe Lei , Dapeng Zhao
To better understand the deep structure and geodynamics of the Datong volcanic field, we apply the receiver-function CCP stacking method to investigate the Moho depth variations in the study area. We use continuous teleseismic waveforms recorded by an ultra-dense, short-period seismic array consisting of 291 stations with an average inter-station distance of ∼5 km, which were deployed for ∼40 days during August to September 2023. After the sedimentary layer correction, detailed depth variations of the Moho discontinuity are revealed beneath the 191 stations in the study area. Our results show that the Moho depth across the entire study area ranges from ∼36 to 44 km. Beneath the Liulengshan mountain, the Moho is relatively deep, reaching a depth of ∼42 km. There are significant variations in the Moho depth on both sides of the Liulengshan piedmont fault. In contrast, beneath the Datong volcanic area, the Moho is, notably shallower, at depths of ∼36 to 40 km. Additionally, the Moho is significantly shallow in a NW-SE oriented zone, which is well consistent with the Datong volcanic field, and there is a nearly E-W shallow Moho zone, which is required to further investigate. The Moho depth variations may be related to the upwelling of hot asthenospheric material, which may lead to the crustal thinning. The hot material upwelling may be related to the India-Asia collision and the combined effects of the westward subduction of the Pacific plate and a deep mantle plume. Our results shed new light on the deep origin and geodynamic processes of the Datong volcanoes.
{"title":"Fine structure of the Moho discontinuity under the Datong volcanic field inferred from a short-period ultra-dense seismic array","authors":"Hao Zhang , Jianshe Lei , Dapeng Zhao","doi":"10.1016/j.pepi.2026.107516","DOIUrl":"10.1016/j.pepi.2026.107516","url":null,"abstract":"<div><div>To better understand the deep structure and geodynamics of the Datong volcanic field, we apply the receiver-function CCP stacking method to investigate the Moho depth variations in the study area. We use continuous teleseismic waveforms recorded by an ultra-dense, short-period seismic array consisting of 291 stations with an average inter-station distance of ∼5 km, which were deployed for ∼40 days during August to September 2023. After the sedimentary layer correction, detailed depth variations of the Moho discontinuity are revealed beneath the 191 stations in the study area. Our results show that the Moho depth across the entire study area ranges from ∼36 to 44 km. Beneath the Liulengshan mountain, the Moho is relatively deep, reaching a depth of ∼42 km. There are significant variations in the Moho depth on both sides of the Liulengshan piedmont fault. In contrast, beneath the Datong volcanic area, the Moho is, notably shallower, at depths of ∼36 to 40 km. Additionally, the Moho is significantly shallow in a NW-SE oriented zone, which is well consistent with the Datong volcanic field, and there is a nearly E-W shallow Moho zone, which is required to further investigate. The Moho depth variations may be related to the upwelling of hot asthenospheric material, which may lead to the crustal thinning. The hot material upwelling may be related to the India-Asia collision and the combined effects of the westward subduction of the Pacific plate and a deep mantle plume. Our results shed new light on the deep origin and geodynamic processes of the Datong volcanoes.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"372 ","pages":"Article 107516"},"PeriodicalIF":1.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147401281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-18DOI: 10.1016/j.pepi.2026.107519
Mohammad Raeesi , Ahmad Zamani , Mohammad Reza Gheitanchi
The 6 November 1990 Furg earthquake is the only documented seismic event in the Zagros Mountains to generate a surface rupture, despite the frequent occurrence of instrumentally recorded earthquakes in the region. This event may provide important insights into the tectonic evolution of the High Zagros. In this study, we detail a 15-km-long surface rupture with ∼2.8 m of slip. The derived slip distribution indicates a shallow rupture and suggests the presence of an asperity at a depth of approximately 7 km, which likely impeded the shallower rupture until the earthquake occurred. Stress change analysis derived from slip distribution shows a robust correlation with the location of large collapse structures within a limited area.
{"title":"The 1990 November 6 Furg (Hormuzgan) earthquake: A rare case of coseismic surface faulting in the Zagros Mountains, Iran—Revisited","authors":"Mohammad Raeesi , Ahmad Zamani , Mohammad Reza Gheitanchi","doi":"10.1016/j.pepi.2026.107519","DOIUrl":"10.1016/j.pepi.2026.107519","url":null,"abstract":"<div><div>The 6 November 1990 Furg earthquake is the only documented seismic event in the Zagros Mountains to generate a surface rupture, despite the frequent occurrence of instrumentally recorded earthquakes in the region. This event may provide important insights into the tectonic evolution of the High Zagros. In this study, we detail a 15-km-long surface rupture with ∼2.8 m of slip. The derived slip distribution indicates a shallow rupture and suggests the presence of an asperity at a depth of approximately 7 km, which likely impeded the shallower rupture until the earthquake occurred. Stress change analysis derived from slip distribution shows a robust correlation with the location of large collapse structures within a limited area.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"372 ","pages":"Article 107519"},"PeriodicalIF":1.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147401282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-18DOI: 10.1016/j.pepi.2026.107520
Cong Ji, Zhouchuan Huang
Shanxi Rift is a typical intracontinental rift developing within North China Craton in the Cenozoic. Its crustal deformation is essential for studying the initiation and development of the intracontinental rift system as well as interactions between a stable cratonic block and an active rift. Here, we study the crustal anisotropy to constrain the crustal deformation of the Shanxi Rift and further discuss the mechanism of the intracontinental rift zone. First, we used the receiver function, − κ stacking method, and harmonic decomposition to reveal the crustal structure of the Shanxi Rift. Then, we retrieved the crustal anisotropy from the receiver functions, particularly using a newly developed iterative weighted least-square fitting method for crustal anisotropy. The results show complex patterns of the crustal anisotropy, indicating multiple factors that control the development of the Shanxi Rift. In the southern part, the dominant fast polarization directions (FPDs) are NNE-SSW across the Ordos Block, the rift zone and the Taihangshan Mountain from west to east while the delay times in the rift zone are slightly larger. The observed anisotropy can be explained by the amalgamation between the western and eastern North China Craton along the Trans-North China Orogen. The Cenozoic rift process strengthened anisotropy in the rift zone but did not change the crustal structures in the adjacent blocks. The rigid rotation of the Ordos Block driven by far-field effect of the Indo-Asian collision plays an important role in this process. In the northern part, the variations in the block and rift zones are remarkable. Dominant NE-SW FPDs in the northern Ordos Block is parallel to the lineation of magnetic anomalies, indicating they mainly reflect fossil anisotropy. However, the FPDs in the northern Shanxi Rift are scattered. The volcanism in the northern rift zone is strong, therefore, we propose the Cenozoic volcanism related to the subduction of the Pacific Plate has altered the crustal structures of the northern Shanxi Rift. These results shed new light on the differential evolution of the intracontinental rift due to varied deep processes.
{"title":"Azimuthal crustal anisotropy of the Shanxi Rift Zone, North China: Implication for the mechanism of intracontinental rift","authors":"Cong Ji, Zhouchuan Huang","doi":"10.1016/j.pepi.2026.107520","DOIUrl":"10.1016/j.pepi.2026.107520","url":null,"abstract":"<div><div>Shanxi Rift is a typical intracontinental rift developing within North China Craton in the Cenozoic. Its crustal deformation is essential for studying the initiation and development of the intracontinental rift system as well as interactions between a stable cratonic block and an active rift. Here, we study the crustal anisotropy to constrain the crustal deformation of the Shanxi Rift and further discuss the mechanism of the intracontinental rift zone. First, we used the receiver function, <span><math><mi>H</mi></math></span> − κ stacking method, and harmonic decomposition to reveal the crustal structure of the Shanxi Rift. Then, we retrieved the crustal anisotropy from the receiver functions, particularly using a newly developed iterative weighted least-square fitting method for crustal anisotropy. The results show complex patterns of the crustal anisotropy, indicating multiple factors that control the development of the Shanxi Rift. In the southern part, the dominant fast polarization directions (FPDs) are NNE-SSW across the Ordos Block, the rift zone and the Taihangshan Mountain from west to east while the delay times in the rift zone are slightly larger. The observed anisotropy can be explained by the amalgamation between the western and eastern North China Craton along the Trans-North China Orogen. The Cenozoic rift process strengthened anisotropy in the rift zone but did not change the crustal structures in the adjacent blocks. The rigid rotation of the Ordos Block driven by far-field effect of the Indo-Asian collision plays an important role in this process. In the northern part, the variations in the block and rift zones are remarkable. Dominant NE-SW FPDs in the northern Ordos Block is parallel to the lineation of magnetic anomalies, indicating they mainly reflect fossil anisotropy. However, the FPDs in the northern Shanxi Rift are scattered. The volcanism in the northern rift zone is strong, therefore, we propose the Cenozoic volcanism related to the subduction of the Pacific Plate has altered the crustal structures of the northern Shanxi Rift. These results shed new light on the differential evolution of the intracontinental rift due to varied deep processes.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"372 ","pages":"Article 107520"},"PeriodicalIF":1.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147401280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-06DOI: 10.1016/j.pepi.2026.107515
Cijin Zhou , Johannes Buchen , Vasilije V. Dobrosavljevic , Benjamin Strozewski , Olivia S. Pardo , Wolfgang Sturhahn , Takayuki Ishii , Thomas S. Toellner , John D. Wilding , Stella Chariton , Bora Kalkan , Martin Kunz , Jennifer M. Jackson
<div><div>We present experimental constraints on the equation of state of a low-sulfur Fe-Ni alloy which contains about 1 wt% sulfur. High-pressure powder X-ray diffraction experiments on <span><math><mrow><msub><mrow><mtext>Fe</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>89</mn></mrow></msub><msub><mrow><mtext>Ni</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>09</mn></mrow></msub><msub><mrow><mtext>S</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>02</mn></mrow></msub></mrow></math></span> were performed at 300 K to a pressure of 143.5 GPa using helium as the pressure-transmitting medium and tungsten as the pressure marker. A pressure-induced <em>bcc–hcp</em> phase transition was constrained to pressures between 13.4 GPa and 19.8 GPa. Our experimental results show that the incorporation of 0.92 wt% sulfur leads to a volume crossover with <em>hcp</em>-<span><math><mrow><msub><mrow><mtext>Fe</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>91</mn></mrow></msub><msub><mrow><mtext>Ni</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>09</mn></mrow></msub></mrow></math></span> at 85 GPa. Above 130 GPa, the <em>hcp</em>-<span><math><mrow><msub><mrow><mtext>Fe</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>89</mn></mrow></msub><msub><mrow><mtext>Ni</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>09</mn></mrow></msub><msub><mrow><mtext>S</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>02</mn></mrow></msub></mrow></math></span> alloy is denser, and its bulk sound speed is slower than that of <em>hcp</em>-<span><math><mrow><msub><mrow><mtext>Fe</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>91</mn></mrow></msub><msub><mrow><mtext>Ni</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>09</mn></mrow></msub></mrow></math></span>, contradicting previously proposed effects of sulfur in Fe(-Ni) alloys as derived from sulfur-rich iron-alloys. Fitting pressure–volume data to the Vinet equation of state yields <span><math><mrow><msub><mrow><mi>V</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>=</mo><mtext>22.449(37)</mtext></mrow></math></span> <!--> <span><math><msup><mrow><mtext>Å</mtext></mrow><mrow><mn>3</mn></mrow></msup></math></span>, <span><math><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>T</mi><mn>0</mn></mrow></msub><mo>=</mo><mtext>184.2(43)</mtext><mspace></mspace><mi>GPa</mi></mrow></math></span>, and <span><math><mrow><msubsup><mrow><mi>K</mi></mrow><mrow><mi>T</mi><mn>0</mn></mrow><mrow><mo>′</mo></mrow></msubsup><mo>=</mo><mtext>4.45(10)</mtext></mrow></math></span> for the <em>hcp</em>-phase, and <span><math><mrow><msub><mrow><mi>V</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>=</mo><mtext>23.798(2)</mtext></mrow></math></span> <!--> <span><math><msup><mrow><mtext>Å</mtext></mrow><mrow><mn>3</mn></mrow></msup></math></span>, <span><math><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>T</mi><mn>0</mn></mrow></msub><mo>=</mo><mtext>153.1(52)</mtext></mrow></math></span> GPa, and <span><math><mrow><msubsup><mrow><mi>K</mi></mrow><mrow><mi>T</mi><mn>0</mn></mrow><mrow><mo>′</mo></mrow></msubsup><mo
{"title":"Equation of state of a low-sulfur iron–nickel alloy up to 143 GPa","authors":"Cijin Zhou , Johannes Buchen , Vasilije V. Dobrosavljevic , Benjamin Strozewski , Olivia S. Pardo , Wolfgang Sturhahn , Takayuki Ishii , Thomas S. Toellner , John D. Wilding , Stella Chariton , Bora Kalkan , Martin Kunz , Jennifer M. Jackson","doi":"10.1016/j.pepi.2026.107515","DOIUrl":"10.1016/j.pepi.2026.107515","url":null,"abstract":"<div><div>We present experimental constraints on the equation of state of a low-sulfur Fe-Ni alloy which contains about 1 wt% sulfur. High-pressure powder X-ray diffraction experiments on <span><math><mrow><msub><mrow><mtext>Fe</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>89</mn></mrow></msub><msub><mrow><mtext>Ni</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>09</mn></mrow></msub><msub><mrow><mtext>S</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>02</mn></mrow></msub></mrow></math></span> were performed at 300 K to a pressure of 143.5 GPa using helium as the pressure-transmitting medium and tungsten as the pressure marker. A pressure-induced <em>bcc–hcp</em> phase transition was constrained to pressures between 13.4 GPa and 19.8 GPa. Our experimental results show that the incorporation of 0.92 wt% sulfur leads to a volume crossover with <em>hcp</em>-<span><math><mrow><msub><mrow><mtext>Fe</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>91</mn></mrow></msub><msub><mrow><mtext>Ni</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>09</mn></mrow></msub></mrow></math></span> at 85 GPa. Above 130 GPa, the <em>hcp</em>-<span><math><mrow><msub><mrow><mtext>Fe</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>89</mn></mrow></msub><msub><mrow><mtext>Ni</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>09</mn></mrow></msub><msub><mrow><mtext>S</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>02</mn></mrow></msub></mrow></math></span> alloy is denser, and its bulk sound speed is slower than that of <em>hcp</em>-<span><math><mrow><msub><mrow><mtext>Fe</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>91</mn></mrow></msub><msub><mrow><mtext>Ni</mtext></mrow><mrow><mn>0</mn><mo>.</mo><mn>09</mn></mrow></msub></mrow></math></span>, contradicting previously proposed effects of sulfur in Fe(-Ni) alloys as derived from sulfur-rich iron-alloys. Fitting pressure–volume data to the Vinet equation of state yields <span><math><mrow><msub><mrow><mi>V</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>=</mo><mtext>22.449(37)</mtext></mrow></math></span> <!--> <span><math><msup><mrow><mtext>Å</mtext></mrow><mrow><mn>3</mn></mrow></msup></math></span>, <span><math><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>T</mi><mn>0</mn></mrow></msub><mo>=</mo><mtext>184.2(43)</mtext><mspace></mspace><mi>GPa</mi></mrow></math></span>, and <span><math><mrow><msubsup><mrow><mi>K</mi></mrow><mrow><mi>T</mi><mn>0</mn></mrow><mrow><mo>′</mo></mrow></msubsup><mo>=</mo><mtext>4.45(10)</mtext></mrow></math></span> for the <em>hcp</em>-phase, and <span><math><mrow><msub><mrow><mi>V</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>=</mo><mtext>23.798(2)</mtext></mrow></math></span> <!--> <span><math><msup><mrow><mtext>Å</mtext></mrow><mrow><mn>3</mn></mrow></msup></math></span>, <span><math><mrow><msub><mrow><mi>K</mi></mrow><mrow><mi>T</mi><mn>0</mn></mrow></msub><mo>=</mo><mtext>153.1(52)</mtext></mrow></math></span> GPa, and <span><math><mrow><msubsup><mrow><mi>K</mi></mrow><mrow><mi>T</mi><mn>0</mn></mrow><mrow><mo>′</mo></mrow></msubsup><mo","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"372 ","pages":"Article 107515"},"PeriodicalIF":1.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Deccan Volcanic Province in western India experienced an intense earthquake swarm comprising more than 10,000 micro-earthquakes (M ≤ 4.1) between November 2018 and May 2024. These events are concentrated within a ∼ 12 km × 6 km area at shallow depths (≤15.0 km). We present a 3-D seismic tomography model that reveals distinctive anomalies in seismic velocities (Vp, Vs), Poisson's ratio (σ), and crack attributes (ε, ξ, and ᴪ) in the focal region. The results indicate low-Vp, low-Vs, high-σ zones, combined with low-ᴪ, high-ε, and high- anomalies, suggesting a highly fluid-filled, fractured rock matrix. These features imply enhanced pore pressure, high porosity, and weakened rock strength, facilitating fault reactivation and earthquake swarm activity. The connectivity of fracture networks to the surface and intersections of lineaments appears to play a key role in stress redistribution and earthquake swarm triggering. Our findings provide insights into the structural and hydromechanical conditions that govern intraplate earthquake swarms in the volcanic provinces of western India, thereby contributing to a deeper understanding of fluid fault interactions within continental interiors. Possible triggering mechanisms include a reduction in effective normal stress at hypocentral depth and hydrolytic weakening of minerals.
2018年11月至2024年5月，印度西部的德干火山省经历了一次强烈的地震群，包括1万多次微地震（M≤4.1）。这些事件集中在浅层深度（≤15.0 km）约12 km × 6 km的区域内。我们提出了一个三维地震层析模型，该模型揭示了震源区域地震速度（Vp, Vs），泊松比（σ）和裂缝属性（ε， ξ和ᴪ）的独特异常。结果表明：低vp、低vs、高σ带，并伴有低ᴪ、高ε、高ξ异常，表明岩石基质具有高充液性、裂隙性。这些特征意味着孔隙压力增大，孔隙度高，岩石强度减弱，有利于断层再活化和地震群活动。断裂网络与地表的连通性和断层线的相交似乎在应力重分布和地震群触发中起着关键作用。我们的发现提供了对控制印度西部火山省板内地震群的结构和流体力学条件的见解，从而有助于更深入地了解大陆内部的流体断层相互作用。可能的触发机制包括下中心深度有效正常应力的降低和矿物的水解弱化。
{"title":"Seismic velocity structure and crack attributes in focal area of earthquake swarm beneath the Deccan Volcanic Province, Western India","authors":"Ajay Pratap Singh, Prabhat Pandey, Yashpal Singh Tomar, Nitesh Kumar Singh, Om Prakash Mishra","doi":"10.1016/j.pepi.2026.107517","DOIUrl":"10.1016/j.pepi.2026.107517","url":null,"abstract":"<div><div>The Deccan Volcanic Province in western India experienced an intense earthquake swarm comprising more than 10,000 micro-earthquakes (M ≤ 4.1) between November 2018 and May 2024. These events are concentrated within a ∼ 12 km × 6 km area at shallow depths (≤15.0 km). We present a 3-D seismic tomography model that reveals distinctive anomalies in seismic velocities (Vp, Vs), Poisson's ratio (σ), and crack attributes (ε, ξ, and ᴪ) in the focal region. The results indicate low-Vp, low-Vs, high-σ zones, combined with low-ᴪ, high-ε, and high-<span><math><mi>ξ</mi></math></span> anomalies, suggesting a highly fluid-filled, fractured rock matrix. These features imply enhanced pore pressure, high porosity, and weakened rock strength, facilitating fault reactivation and earthquake swarm activity. The connectivity of fracture networks to the surface and intersections of lineaments appears to play a key role in stress redistribution and earthquake swarm triggering. Our findings provide insights into the structural and hydromechanical conditions that govern intraplate earthquake swarms in the volcanic provinces of western India, thereby contributing to a deeper understanding of fluid fault interactions within continental interiors. Possible triggering mechanisms include a reduction in effective normal stress at hypocentral depth and hydrolytic weakening of minerals.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"372 ","pages":"Article 107517"},"PeriodicalIF":1.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147401283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2026-01-06DOI: 10.1016/j.pepi.2026.107500
A.V. Satyakumar , M. Venkateshwarlu
We report the outcomes of the anisotropy of magnetic susceptibility (AMS), rock magnetic properties, and microscopic observations of the Ladakh Batholith (LB). Our magnetic mineralogy reveals that Ti-magnetite pseudo-single domain is the main magnetic mineral, with other minerals including quartz, biotite, and feldspar. AMS study reveals that the magnetic fabric is reliable for ∼NW-SE trending magma flow. Notably, we see established magnetic lineation and foliation, as well as major susceptibility axes that are well-grouped and exhibit a triaxial distribution regardless of their shape factor (T). Magma flow direction is inferred from the magnetic fabric orientation, i.e., the direction of maximal susceptibility, K1. Concentric magnetic lineations and foliations appear to follow the boundaries of plutons and mostly represent the movements of magma chambers. This study reveals that the LB may have grown due to multi-stage interactions between host Ladakh granitoids and several pulses of coeval mafic and felsic magmas.
{"title":"Ladakh batholith emplacement mechanism based on analysis of magnetic fabric and mineralogy","authors":"A.V. Satyakumar , M. Venkateshwarlu","doi":"10.1016/j.pepi.2026.107500","DOIUrl":"10.1016/j.pepi.2026.107500","url":null,"abstract":"<div><div>We report the outcomes of the anisotropy of magnetic susceptibility (AMS), rock magnetic properties, and microscopic observations of the Ladakh Batholith (LB). Our magnetic mineralogy reveals that Ti-magnetite pseudo-single domain is the main magnetic mineral, with other minerals including quartz, biotite, and feldspar. AMS study reveals that the magnetic fabric is reliable for ∼NW-SE trending magma flow. Notably, we see established magnetic lineation and foliation, as well as major susceptibility axes that are well-grouped and exhibit a triaxial distribution regardless of their shape factor (T). Magma flow direction is inferred from the magnetic fabric orientation, i.e., the direction of maximal susceptibility, K<sub>1</sub>. Concentric magnetic lineations and foliations appear to follow the boundaries of plutons and mostly represent the movements of magma chambers. This study reveals that the LB may have grown due to multi-stage interactions between host Ladakh granitoids and several pulses of coeval mafic and felsic magmas.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"371 ","pages":"Article 107500"},"PeriodicalIF":1.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145915309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2026-01-22DOI: 10.1016/j.pepi.2026.107502
Nicolás P. Müller , Christophe Gissinger , François Pétrélis
We study the process of magnetic reversals in the presence of a stably-stratified layer below the core-mantle boundary using direct numerical simulations of the incompressible magnetohydrodynamics equations under the Boussinesq approximation in a spherical shell. We show that the dipolar-multipolar transition shifts to larger Rayleigh numbers in the presence of a stably-stratified layer, and that the dipolar strength of the magnetic field at the core-mantle boundary increases due to the skin effect. By imposing an heterogeneous heat flux at the outer boundary, we break the equatorial symmetry of the flow, and show that different heat flux patterns can trigger different dynamo solutions, such as hemispheric dynamos and polarity reversals. Using kinematic dynamo simulations, we show that the stably-stratified layer leads to similar growth rates of the dipole and quadrupole components of the magnetic field, playing the role of a conducting boundary layer, favouring magnetic reversals, and a dynamics predicted by low-dimensional models.
{"title":"Magnetic reversals in a geodynamo model with a stably–stratified layer","authors":"Nicolás P. Müller , Christophe Gissinger , François Pétrélis","doi":"10.1016/j.pepi.2026.107502","DOIUrl":"10.1016/j.pepi.2026.107502","url":null,"abstract":"<div><div>We study the process of magnetic reversals in the presence of a stably-stratified layer below the core-mantle boundary using direct numerical simulations of the incompressible magnetohydrodynamics equations under the Boussinesq approximation in a spherical shell. We show that the dipolar-multipolar transition shifts to larger Rayleigh numbers in the presence of a stably-stratified layer, and that the dipolar strength of the magnetic field at the core-mantle boundary increases due to the skin effect. By imposing an heterogeneous heat flux at the outer boundary, we break the equatorial symmetry of the flow, and show that different heat flux patterns can trigger different dynamo solutions, such as hemispheric dynamos and polarity reversals. Using kinematic dynamo simulations, we show that the stably-stratified layer leads to similar growth rates of the dipole and quadrupole components of the magnetic field, playing the role of a conducting boundary layer, favouring magnetic reversals, and a dynamics predicted by low-dimensional models.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"371 ","pages":"Article 107502"},"PeriodicalIF":1.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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