Tectonophysics最新文献

{"title":"Rupture behaviors of the southern Xianshuihe fault and seismicity around Mt. Gongga: Insights from the 2022 MW 6.6 Luding (China) earthquake sequence","authors":"Wenzheng Gong ,&nbsp;Lingling Ye ,&nbsp;Shiqing Xu ,&nbsp;Yipei Tan ,&nbsp;Xiaofei Chen","doi":"10.1016/j.tecto.2024.230538","DOIUrl":"10.1016/j.tecto.2024.230538","url":null,"abstract":"<div><div>The 2022 <em>M</em>_<em>W</em> 6.6 Luding earthquake occurred on the Moxi segment of the Xianshuihe fault at the southeast margin of Tibetan Plateau, China. To assess the seismic potential of the Moxi segment, we examine the rupture process of the mainshock and aftershock sequence, along with historical seismicity. Our preferred slip model inverted from teleseismic body waves and regional GNSS static displacements shows a dominant southeastward rupture consisting of two distinct, prominent slip patches along strike extending by ∼15 km, with a peak slip of ∼2.8 m, approximately balancing the slip deficit since the last major earthquake in 1786. The northern section of the Moxi segment experienced minor coseismic slip, which, together with the significant slip deficits and positive Coulomb failure stress change induced by the 2022 mainshock indicates a high seismic potential. Several aftershock clusters are distributed along or near the Moxi segment, with strike-slip focal mechanisms around the downdip edge of the coseismic slip area at ∼8‐12 km. At the eastern flank of Mt. Gongga, another cluster of normal faulting aftershocks is located at shallower depths of ∼3‐7 km, with high seismicity rate over ∼9 months including two other M5 sequences in January and February 2023. Similar intense shallow normal faulting activity had occurred after the impoundment of the nearby Dagangshan reservoir in 2015. We speculate that some NW-SE trending normal faults were initially developed by the gravitational collapse of Mt. Gongga underneath the eastern flank, further weakened by fluid flow, as supported by the existence of hot springs and water impoundment, and reactivated by the tensional stress change induced by the 2022 mainshock. These results have important implications for assessing the seismic hazard in and around the Moxi segment, and the potential interplay between strike-slip fault and nearby mountain areas.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"892 ","pages":"Article 230538"},"PeriodicalIF":2.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552849","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}

{"title":"Fault strength, healing and stability in the Nankai Trough accretionary prism off Kii Peninsula, Japan, as illustrated by friction experiments on gouge of a cored sample","authors":"Kyuichi Kanagawa,&nbsp;Junya Fujimori ,&nbsp;Tomoya Nakanishi ,&nbsp;Sayumi Sagano ,&nbsp;Michiyo Sawai","doi":"10.1016/j.tecto.2024.230526","DOIUrl":"10.1016/j.tecto.2024.230526","url":null,"abstract":"<div><div>In order to investigate fault strength, healing and stability in the Nankai Trough accretionary prism off Kii Peninsula, Japan, we conducted two series of triaxial friction experiments on gouge of a silty-claystone sample cored from 2183.6 mbsf (meters below seafloor) at IODP Site C0002, at confining pressure (<em>P</em>_c), pore-water pressure (<span><math><msub><mi>P</mi><mrow><msub><mi>H</mi><mn>2</mn></msub><mi>O</mi></mrow></msub></math></span>) and temperature (<em>T</em>) conditions simulating those <em>in situ</em> at 1000–6000 mbsf there; rate-stepping tests at axial displacement rates (<em>V</em>_axial) changed stepwise among 0.1, 1 and 10 μm/s, and slide-hold-slide tests at <em>V</em>_axial = 1 μm/s with hold time (<em>t</em>_h) ranging from 10 to 10⁴ s.</div><div>Experimentally determined steady-state and static friction coefficients, <em>μ</em>_ss and <em>μ</em>_s, respectively, and the log-linear <em>t</em>_h dependence of frictional healing, <em>β</em>, exhibit a decrease with simulated depth down to 3000 mbsf at which condition <em>T</em> was 100 °C, followed by an increase toward 6000 mbsf. On the other hand, the rate dependence of <em>μ</em>_ss<em>, a</em> – <em>b</em>, gradually decreases with simulated depth, changing from positive at ≤4000 mbsf through ∼0 at 5000 mbsf to negative at 6000 mbsf at which condition stick slips were observed.</div><div>Our experimental results suggest the presence of a low fault-strength and weak fault-healing zone at ∼3000 mbsf beneath IODP Site C0002, possibly due to elevated pore pressure induced by smectite dehydration. This zone correlates well with the previously reported low seismic-velocity zone and the source area of very low-frequency earthquakes to the south. Our experimental results also suggest that faulting beneath IODP Site C0002 is stable and aseismic at ≤4000 mbsf, transitional at 5000 mbsf, and potentially unstable and seismic at 6000 mbsf. In fact, stick slips corresponding to seismic faulting were observed at the 6000 mbsf condition. This implies that faulting along the plate-boundary thrust located at ∼5200 mbsf beneath IODP Site C0002 is potentially seismogenic.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"893 ","pages":"Article 230526"},"PeriodicalIF":2.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578718","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}

{"title":"Tectonics of the Mw 6.8 Al Haouz earthquake (Morocco) reveals minor role of asthenospheric upwelling","authors":"Marco G. Malusà ,&nbsp;Alessandro Ellero ,&nbsp;Giuseppe Ottria","doi":"10.1016/j.tecto.2024.230533","DOIUrl":"10.1016/j.tecto.2024.230533","url":null,"abstract":"<div><div>A reliable identification of the fault responsible for the magnitude 6.8 Al Haouz earthquake that struck Morocco on 8 September 2023 has so far been hampered by a lack of accurate tectonic analyses. Here we provide the first updated tectonic framework of the earthquake epicentral area based on original field data. We cast our results into the context of available geomorphological, thermochronological and geophysical constraints, and discuss the earthquake characteristics within the framework of competing tectonic models either based on asthenospheric upwelling or transpressional tectonics. We found that the Al Haouz earthquake was likely generated by rupture along a north-dipping high-angle fault, linking former fault planes belonging to an orogen-scale WSW-ESE transpressional shear zone. The geological evolution and seismotectonic structure of the region are largely governed by the oblique convergence of tectonic plates. The impact of asthenospheric upwelling, if any, remains limited and may only influence the geomorphological evolution of the Western High Atlas, but cannot explain the seismotectonic and geological features observed today at the surface, which are instead effects of transpressional tectonics.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"891 ","pages":"Article 230533"},"PeriodicalIF":2.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142442748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shale gas leakage and fault activation: Insight from the 2021 Luxian MS 6.0 earthquake, China","authors":"Zhaofei Liu ,&nbsp;Zhi Chen ,&nbsp;Ying Li ,&nbsp;Zhidan Zhao ,&nbsp;Shunying Hong ,&nbsp;Le Hu ,&nbsp;Ling Ma ,&nbsp;Chang Lu ,&nbsp;Yuanxin Zhao ,&nbsp;Hongyi He ,&nbsp;Shujuan Su ,&nbsp;Ying Zhao ,&nbsp;Weiye Shao ,&nbsp;Zhengyang Cao ,&nbsp;Hanyu Wang","doi":"10.1016/j.tecto.2024.230530","DOIUrl":"10.1016/j.tecto.2024.230530","url":null,"abstract":"<div><div>In the region of large gas fields, extensive research has been conducted on earthquakes induced by industrial production in shale gas fields. However, limited attention has been given to the impact of post-earthquake events on shale gas reservoir leakage and fault activation. The Luxian <em>M</em>_S 6.0 earthquake, which occurred on 16 September 2021 in the Luzhou shale gas field, has raised concerns about post-earthquake shale gas leakage. Post-earthquake measurements of soil gases (Rn, CO₂, CH₄, and H₂) and isotopic analyses (δ¹³C_CO2, δ¹³C_CH4 and δD_CH4) in the Luzhou shale gas field area reveal that the Huayingshan fault zone, a natural pathway for shale gas leakage, was not activated by the Luxian earthquake and did not exhibit any further shale gas leakage after the 2021 earthquake. Furthermore, the seismogenic fault, which was impacted by the earthquake, did not damage the shale gas reservoir, causing shale gas leakage. This study provides an important foundation for future research on shale gas extraction and seismic activity in the region.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"891 ","pages":"Article 230530"},"PeriodicalIF":2.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438156","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}

{"title":"A numerical study of contemporary crustal deformation partitioning across the Southwestern Tian Shan orogen","authors":"Weilin Kong ,&nbsp;Luyuan Huang ,&nbsp;Yebo Li ,&nbsp;Yiwei Tian","doi":"10.1016/j.tecto.2024.230529","DOIUrl":"10.1016/j.tecto.2024.230529","url":null,"abstract":"<div><div>The Tian Shan region is a typical example of crustal deformation within an intracontinental environment, where the lithospheric rheological properties are marked by significant spatial heterogeneity. However, the role of lithospheric rheology in crustal strain partitioning within the interior of the Tian Shan orogenic belt remains nebulous. Here, we utilized a two-dimensional viscoplastic model with contact elements constrained by GPS velocities and fault slip rates to investigate the influence of the block's strength on crustal deformation in the southwestern Tian Shan region. Our founding suggests that a weaker lower crust beneath the northern Tian Shan region offers a potential mechanism for the contemporary deformation patterns. Contemporary crustal deformation at Tian Shan is mainly concentrated along the piedmont thrust-and-fold belts and diffuses in the orogen's interior. This pattern of crustal strain partitioning is closely linked to the interplay between fault slips and lithospheric deformation. This finding emphasizes the significant role that the lithospheric rheology and pre-existing faults played in the deformation partitioning in the interior of the Tian Shan orogeny.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"891 ","pages":"Article 230529"},"PeriodicalIF":2.7,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142437925","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}

{"title":"Spatially varying stress regime in the southern Junggar Basin, NW China","authors":"Lin Wu ,&nbsp;Xingqiang Feng ,&nbsp;Lei Zhou ,&nbsp;Shuwei Guan ,&nbsp;Dongsheng Ji ,&nbsp;Yuanlong Tan ,&nbsp;Linyan Zhang","doi":"10.1016/j.tecto.2024.230516","DOIUrl":"10.1016/j.tecto.2024.230516","url":null,"abstract":"<div><div>The southern Junggar Basin in NW China is an important tectonic unit in the region of the Tibetan Plateau and has been the focus of considerable research into its tectonic processes and geodynamic setting. However, the relationship between deep structural deformation and stress in this region remains unclear. This study investigates the Gaoquan and Hutubi anticlines in the southern Junggar Basin using three-dimensional geophysical data and a finite-element numerical simulation to examine the crustal stress distribution and stress regime at depths of up to 7 km. Numerical simulation results indicate that the stress regime in the southern Junggar Basin changes from west to east. In the western part of the region, including the Gaoquan anticline at depths of 4900–6100 m, the maximum horizontal principal stress shows a peak of 140–200 MPa, the minimum horizontal principal stress is 110–170 MPa, and the vertical principal stress is 115–175 MPa, indicating a mixed stress regime incorporating both compression and strike-slip components. In the eastern part of the region, including the Hutubi anticline at depths of 5400–7800 m, the maximum horizontal principal stress shows a peak of 160–280 MPa, the minimum horizontal principal stress is 155–250 MPa, and the vertical principal stress is 125–215 MPa, indicating a compressive stress regime. The stress magnitude and orientation are affected by the presence of faults and depth in the crust. Combining these results with the regional tectonic setting, it is considered that the geometrical relationship between pre-existing faults and the current stress field is the main control on the west–east differentiation in the stress regime, with spatial variations in the mechanical parameters of the crust and the pressure coefficient being secondary factors. These results provide insights into the relationship between stress and deformation, and support the updated version of the World Stress Map database.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"891 ","pages":"Article 230516"},"PeriodicalIF":2.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445894","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}

{"title":"Heterogeneous mineralogical composition and fault behaviour: A systematic study in ternary fault rock compositions","authors":"Roberta Ruggieri ,&nbsp;Giacomo Pozzi ,&nbsp;Giuseppe Volpe ,&nbsp;Francesca Bottazzi ,&nbsp;Marco Brignoli ,&nbsp;Anna Antonia Irene Corradi ,&nbsp;Stefano Mantica ,&nbsp;Lorenzo Osculati ,&nbsp;Stefania Petroselli ,&nbsp;Giorgio Volontè ,&nbsp;Cristiano Collettini","doi":"10.1016/j.tecto.2024.230528","DOIUrl":"10.1016/j.tecto.2024.230528","url":null,"abstract":"<div><div>The heterogeneous mineralogical compositions of fault gouges, formed during fault evolution, influence frictional properties and slip behaviour. While the influence of individual mineral phases on friction has been extensively studied, the impact of varying systematically mineral phases in gouge mixtures on macroscopic frictional behaviour remains unclear. Thus, we performed 34 frictional experiments on fault gouges composed of three representative mineral phases: muscovite (platy phyllosilicate), quartz (granular silicate) and calcite (granular carbonate), known for their markedly distinct frictional properties. Using a biaxial rock deformation apparatus (BRAVA), we performed tests on fault gouges with grain sizes &lt;125 μm under normal stresses of 50–100 MPa, at room temperature and water-saturated conditions. Our data indicate that the mineralogical composition of fault gouges significantly affects frictional strength, healing, and stability with a non-trivial pattern. Increasing the muscovite content leads to a decrease in frictional strength, from 0.62 for pure calcite and 0.56 for pure quartz to 0.33 of pure muscovite, along with reduced frictional healing and a velocity-strengthening behaviour. This weakening is promoted by a transition from localized deformation along discrete shear planes in granular-rich fault gouges to distributed deformation within the entire gouge layer with increasing muscovite content. At fixed muscovite content, frictional properties depend on the dominant granular phase. Calcite-dominated mixtures exhibit more marked frictional weakening rather than quartz-dominated ones, suggesting a non-linear mixing law between friction coefficient and muscovite content. This different trend is likely due to favourable conditions for fluid-assisted pressure-solution of calcite and foliation development, unlike quartz. When only the granular phases are mixed, we observe complex behaviour with the indentation of quartz into calcite, resulting in higher values of healing rates than those of pure end-member mixtures.</div><div>Our findings provide robust insights into microphysical processes strongly dependent on the complex mineralogical compositions usually observed along natural faults.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"891 ","pages":"Article 230528"},"PeriodicalIF":2.7,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529075","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}

{"title":"Recent and active faulting along the exposed front of the Northern Apennines (Italy): New insights from field and geochronological constraints","authors":"Thomas Gusmeo ,&nbsp;Giacomo Carloni ,&nbsp;Gianluca Vignaroli ,&nbsp;Luca Martelli ,&nbsp;Hsun-Ming Hu ,&nbsp;Chuan-Chou Shen ,&nbsp;Giulio Viola","doi":"10.1016/j.tecto.2024.230517","DOIUrl":"10.1016/j.tecto.2024.230517","url":null,"abstract":"<div><div>Establishing genetic links between active shallow faulting and deep seismogenic sources is challenging, especially in areas where seismogenic faults lack clear and readily interpretable geological evidence at the surface. The architecture of the Pedeapenninic margin of the Northern Apennines (Italy) reflects a regional-scale and complex NE-verging blind thrust system, which is dissected by transpressive/transtensive faults resulting from active NE-SW orogenic compression. The local geological framework is defined by allochthonous ocean-derived units resting atop Pliocene-to-present successions exposed along the Northern Apennines margin and to the NE of it, while the innermost chain sector mostly contains Adria-related units. We present results from field structural-geological investigations to identify and characterize potential active faults along the margin. There, the Pliocene-to-present units are faulted and folded, indicating that tectonic activity is still on-going, thus contributing to the local seismic hazard. Top-to-the NE and SW normal faults are common in the area and deform the Pliocene-to-present succession together with NE-SW strike-slip and transpressional/transtensional faults. Based on field evidence, we define four potentially active thrust segments affecting Middle Pleistocene to Holocene deposits exposed along the margin. Calcite U-Th dating on samples from faults extend the most recent datable tectonic activity back to the Middle Pleistocene. Paleostress analysis from inversion of fault-slip data from the most recent identified striated fault planes constrains a NE-SW shortening direction parallel to the Apennines regional migration direction. A distinct but coaxial extensional stress regime, recorded by structures measured within Plio-Pleistocene formations, was also identified. Our results offer a sound starting point for future investigations aimed at improving our understanding of active and seismogenic faulting in the area, so as to create robust Probabilistic Seismic and Fault Displacement Hazard Assessment (PSHA and PFDHA) models that can implement refined seismic hazard maps benefitting from structural-geological deterministic inputs in addition to the classic seismological constraints.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"891 ","pages":"Article 230517"},"PeriodicalIF":2.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphostructural evidence of crustal-scale, active along-strike segmentation of the Umbria-Marche Apennines, Italy","authors":"S. Teloni ,&nbsp;E. Valente ,&nbsp;A. Ascione ,&nbsp;S. Mazzoli ,&nbsp;P.P. Pierantoni ,&nbsp;M.C. Invernizzi","doi":"10.1016/j.tecto.2024.230527","DOIUrl":"10.1016/j.tecto.2024.230527","url":null,"abstract":"<div><div>This paper discusses the response of topography and river networks to non-uniform lithology and tectonic forcing in the Umbria-Marche sector of the Apennines fold and thrust belt. We ruled out the role of variable erosion of rock types and interpret channel steepness data in terms of rock uplift, discovering a southward increase in the total amount of uplift. Such a trend appears as the large-scale response to uneven vertical motions of different sectors of the mountain ridge and foothills. The general coincidence between sector boundaries and transversal, NE-SW striking faults mapped by seismic interpretation in the outer zone of the fold and thrust belt, suggests that such faults extend to the SW, beneath the allochthonous thrust sheets of the mountainous area. Therefore, it may be inferred that such transversal faults represent long-lived, deeply rooted basement structures compartmentalizing both the axial and the outer zones of the fold and thrust belt. We suggest that differential uplift was essentially controlled by variable amounts of basement thrust displacement characterizing the compartmentalized belt. This interpretation deviates from a more conventional view that uplift of the central Apennines, particularly prominent in the south, is dynamically supported. Our results, besides shedding new light into the active tectonic behavior of a large portion of the Italian peninsula, also provide general insights into the surface response to the differential behavior of crustal blocks produced by along-strike segmentation of active mountain belts.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"891 ","pages":"Article 230527"},"PeriodicalIF":2.7,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418536","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}

{"title":"Crustal and uppermost mantle S-velocity structure of the Seoul metropolitan area on the Korean Peninsula from Helmholtz tomography","authors":"Seungwoo Park ,&nbsp;Sung-Joon Chang ,&nbsp;Junhyung Lee ,&nbsp;Dongchan Chung ,&nbsp;Byeongwoo Kim ,&nbsp;Seongjun Park ,&nbsp;Tae-Kyung Hong","doi":"10.1016/j.tecto.2024.230518","DOIUrl":"10.1016/j.tecto.2024.230518","url":null,"abstract":"<div><div>The Seoul metropolitan area, the most densely populated part of the Korean Peninsula, features complex subsurface structures and seismogenic faults, though their characteristics remain ambiguous due to low seismicity and limitations in fault investigation. High-resolution velocity models can provide constraints for identifying subsurface faults by detecting elongated low-velocity anomalies along fault zones. Recently, a dense seismic network was deployed in this area, facilitating the use of Helmholtz tomography, an array-based method that accounts for finite-frequency effects. Utilizing Helmholtz tomography, we obtained a high-resolution S-wave velocity model down to a depth of 50 km with waveform data recorded at 74 broadband seismic stations. We found that a linear low-velocity anomaly along the Pocheon fault extends to the uppermost mantle, with an increasing width with depth. In contrast, the Dongducheon fault, which traverses Seoul from north to south, is not well imaged, indicating its current weak activity. Another linear low-velocity anomaly extends southwest through Seoul from northern Seoul, potentially representing the extension of the Pocheon fault based on similar strike and dip directions. Additionally, a large lateral low-velocity anomaly is identified in the lower crust beneath the northern part of the Seoul metropolitan area, interpreted as a ductile décollement, connected with the Pocheon, Wangsukcheon, and possibly Gyeonggang faults. This study successfully identified the extensions and orientations of subsurface faults beneath the Seoul metropolitan area down to the uppermost mantle, which is critical for seismic hazard predictions and earthquake simulations in this highly populated area.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"891 ","pages":"Article 230518"},"PeriodicalIF":2.7,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}