The subduction and rollback of the Western Pacific Plate and expansion of the Qinghai-Xizang Plateau have significantly influenced the tectonic evolution of the North China Craton (NCC). However, the detailed characteristics of the associated deep dynamic processes remain poorly understood. Seismic anisotropy serves as a key indicator for probing deformation and dynamics in the interior of the Earth. Based on surface wave data recorded by dense seismic arrays, this study applied the Eikonal tomography method to obtain Rayleigh-wave azimuthal anisotropy images at periods of 12-120 s across the central and eastern NCC. We further inverted these data to create a three-dimensional (3D) shear-wave velocity structure and azimuthal anisotropy to a depth of 260 km. Our results revealed a prominent low-velocity anomaly in the upper mantle beneath the central-eastern study region, where the fast direction is primarily E-W. We suggest that this low-velocity anomaly likely originated from the dehydration of the stagnant Western Pacific slab in the upper mantle, which induces partial melting that subsequently ascends to the base of the lithosphere. Furthermore, the E-W anisotropic pattern is likely associated with eastward asthenospheric flow caused by the retreating subduction of the Pacific Plate. East of the Ordos Block, an N-S trending low-velocity anomaly below 180 km depth exhibits weak anisotropy, which may be attributed to deep material upwelling associated with eastward asthenospheric flow and abrupt lateral variations in lithospheric thickness. In the northeastern NCC, the fast direction in the asthenosphere and below shifts to NW-SE, which is distinct from that beneath the North China Plain. This difference may reflect variations in the subduction angle and rollback rate between the Japan and Ryukyu trenches. Our findings provide new observational constraints on lithospheric deformation and deep dynamic processes in this region.

Abstract The 2025 Mw7.1 Dingri earthquake is the largest normal‐faulting event in southern Tibetan plateau recorded with near‐field observations. By integrating back‐projection imaging, multi‐point‐source inversion, and finite‐fault modeling, we reveal that the rupture propagated at variable speeds in a cascading manner across a complex conjugate fault network, generating significant high‐frequency radiation at the fault junction. Near‐field waveforms directly document the slip along the western boundary of the Dengmecuo graben as coseismic. The spatiotemporal evolution of simultaneous rupture along both boundaries of the graben suggests a possible structural connectivity at depth between two conjugate faults. Mainshock nucleation was likely promoted by sustained stress loading following the 2015 Gorkha earthquake, together with local stress perturbations from recent regional earthquakes and the foreshock sequence. These processes bridge long‐term interseismic deformation and the dramatic seismic rupture of the Dingri earthquake, illustrating a typical slow‐to‐fast failure process.

Investigating the spatial distribution of coseismic rupture, postseismic afterslip, and their interactions is essential for understanding the heterogeneous frictional characteristics of faults, and seismic hazard assessments. This study offers a comprehensive analysis of both seismic and aseismic slip of the 2022 MW6.7 Menyuan earthquake, which took place at the western terminus of the Tianzhu seismic gap located in the northeastern Qinghai-Xizang Plateau. By integrating near-field GNSS measurements, InSAR line-of-sight (LOS) displacements, and surface rupture data, we refined the coseismic slip distribution using a kinematic inversion and a mechanically constrained model. Our results reveal an unexpectedly large coseismic slip of about 3.3 m at shallow depths (less than about 6 km), along with minimal shallow slip deficit—features rarely observed in earthquakes of similar magnitude globally. The mechanically constrained approach yields a static stress drop of about 6.4 MPa. Additionally, we invert for the afterslip distribution from cumulative postseismic GNSS displacements recorded during the initial 2.7 years subsequent to the mainshock. The afterslip is predominantly situated downdip of the coseismic rupture zone, releasing 28.5% of the coseismic moment. There is a tight correlation between the spatiotemporal evolution of aftershocks and the downdip afterslip, with limited contributions from viscoelastic relaxation and poroelastic rebound which indicates that the afterslip mechanism primarily controls early postseismic deformation.

Crustal thickness and Poisson's ratio are key indicators of regional isostasy and material composition. Using teleseismic waveform data from 126 permanent stations and 179 temporary stations in the Pamir–West Tianshan region, we obtain the crustal thickness and average Poisson's ratio by the h–κ stacking method. The results show that the crust of the Pamir Plateau is thick in the middle and thin on its eastern and western sides, while the West Tianshan region exhibits a “thin–thick–thin” distribution from south to north. The mountainous regions have thicker crust compared to the intermountain basins which feature relatively thinner crust in West Tianshan. Based on the isostasy state analysis of the Airy model, the equilibrium curves of the Pamir and the West Tianshan are similar. The distribution of Poisson's ratio in the study area is characterized by several east–west oriented bands, forming a “high–low–high” distribution pattern as a whole. Joint geophysical and geochemical studies indicate that regions with high Poisson's ratio often have phenomena such as lithospheric subduction and Moho offsets, these areas also display characteristics such as low velocity, high conductivity, and high surface heat flow, which may be related to local melting materials in the middle and lower crust.

In-depth seismological research relies heavily on the high-resolution community velocity model, andthe study of crustal structure and deep Earth dynamics can be better supported by developing the high-precisioncommunity Moho interface model based on the community velocity model. To further extend the applications ofcommunity velocity model, we develop the community Moho interface model in this study using three new-generation high-resolution velocity models in the Sichuan-Yunnan area. First, we have an initial knowledge onthe response of Moho surface for each station using H-kappa 0 stacking. The receiver function multiple waves cknesses show a significant difference from those results revealed by Deep Seismic Sounding. Three velocitymodels result in inaccurate Moho surface assessment because, according to the distribution images of velocityratios, they have a narrow lateral variation range of wave velocity ratios and significantly diverge from previousstudies. We conducted H-kappa stacking only using VP or VS model in order to obtain a reasonably reliable Mohosurface model. The findings suggest that the VP model is more trustworthy than the VS model since the variationcharacteristics of the acquired crustal thickness are consistent with Deep Seismic Sounding results and thediscrepancy between the overlaid results based on the VP model is relatively minor. As a result, we choose thecrust thickness results using H-kappa stacking of the three VP models, and take their average value as SWChinaCVM-MOHO-2.0

Notwithstanding the evolution of the Tibetan Plateau being a fundamental topic in continental dynamics, general mechanisms of Plateau uplift remain elusive and past Plateau evolution models lack clarity of the actual geodynamical process. Here, with detailed mappings of intra-crustal low-velocity zones and crust-mantle discontinuity in the region using the seismic data consolidated by the China Seismological Reference Model project, we show that the present-day Tibetan Plateau manifests three stages of mid-crustal flow driven evolution that can be clearly identified in three distinct regions of the Plateau: a pre-response stage with a young mid-crustal partially molten zone but little response of surface topography and crust-mantle discontinuity, the first stage with a mature mid-crustal partially molten zone by deepening crust-mantle discontinuity without large-scale surface uplift, and the last stage by large-scale surface uplifting. Our results provide direct observation and a unique reference of geodynamical responses at different evolution stages of the continent-continent collision zones.

On September 16, 2021, an MS 6.0 earthquake struck Luxian County in the Sichuan basin. To investigate the regional velocity structure and its relationship with seismic activity, we gathered seismic phase data from permanent stations for events occurring between January 2009 and April 2021 as well as data from a dense mobile seismic array that operated from April 2021 to July 2023. Utilizing Double-Difference tomography, we have determined well-constrained earthquake relocations and have derived a detailed 3D velocity structure. Many of the earthquakes exhibit linear clustering patterns, with an average depth of 4.3 km and a NE-SW orientation. Approximately 96 % of the seismic events occurred within a depth range of 0-7 km. The early aftershock sequence of the Luxian event also displayed a linear trend, with a length of 6 km but with an ESE orientation. The mainshock occurred at a depth of 6.2 km, located at the northwestern end of the aftershock sequence. The aftershock sequence along with other linear seismic clusters, predominantly occurred within regions characterized by high seismic velocities and low Poisson's ratios, both within the sedimentary cover above the crystalline basement. The heterogeneity of the velocity structure likely plays a significant role in controlling the occurrence of moderate-to-strong earthquakes in the deeper parts of the study region, which deepens the existing understanding from previous research: pre-existing faults, their scales, and their slip-tendencies under the present-day regional and reservoir-scale stress fields are also controlling factors for induced earthquakes, especially larger ones. We have identified five areas where moderate-to-strong earthquakes are speculated to have a higher likelihood of occurrence. These findings hold considerable importance for local seismic hazard assessments.

Utilizing the seismic wave data recorded by temporary and permanent seismic stations deployed in the North China Craton, we obtained the phase velocity images of Rayleigh wave with 15~150 s period in the entire North China Craton by surface wave tomography based on the Eikonal equation, and inverted the S wave velocity structure in the study area. It shows that in the depth range of the upper mantle and lithosphere, the Yanshan area is characterized by high velocity, whereas low-velocity zones are found in the Datong Basin in the central North China Craton and to the south of it, as well as in the Taihang Mountains, which are connected to the low-velocity zone of the North China Basin, showing a large area of low velocity anomaly with the velocity lower than that of the northeastern margin of the Tibetan Plateau. The S-wave velocity shows that the lithospheric thickness of the Ordos block is large; it is close between the central North China Craton and the North China Basin, while larger in the Yanshan area than that in the North China Basin. This study suggests that the lithospheric destruction of the North China Craton is partitioned. There are cratonic destruction in the central North China Craton and the Yanshan area, but the degree of destruction is different. Local destruction is also found in the northern Ordos block, which, however, has little influence on the stability of the craton. The main dynamic source of craton destruction is more likely to be the westward subduction of the Pacific plate. It is found that the distribution of strong earthquakes in the central and eastern parts of the craton coincides with the craton destruction areas, and most of the strong earthquakes occur on the lithospheric strength boundary. The difference in lithospheric strength may be the reason why strong earthquake activity of the lithospheric strength boundary is higher than that of other areas.

On 18 December 2023. at 23:59. the M(s)6. 2 earthquake occurred near the Jishishan Eastern Margin Fault in the southern section of the Lajishan in Jishishan County, Gansu. To investigate this earthquake's seismogenic tectonic and seismogenic environment and the relationship between the aftershock sequences and the deep structure. This paper uses the earthquake event data constructed on permanent stations, warning stations and temporarily deployed dense station arrays, using double difference tomography to carry out earthquake location and three-dimensional velocity structure studies. After relocation, the aftershock sequence spreads approximately in the SE-NW direction with a total length of about 15 km. The depth distribution of the earthquake dominance ranges from 8 similar to 14 km and the average depth is 10.4 km. There is a dislocation in the earthquake depths between the aftershock strip north of the main rupture and the aftershock sequence near the main rupture, and the two dips are approximately vertical in space. The northeast-dipping Dahejia fault is the seismogenic fault of the main rupture, and the aftershock strip north of the main rupture presumably occurred on a southwest-dipping recoil blind fault. The aftershock sequences basically occurred within the high-velocity and low Poisson's ratio anomalies, the high-velocity anomalies and the aftershock sequences are highly coincident. The non-uniformity of the velocity structure is the main deep tectonic factor controlling the pattern of this earthquake and aftershocks. This earthquake was supposed to be a typical recoil-type event that occurred in the context of extrusion tectonics, with stress accumulation and release within a high-velocity and low Poisson's ratio anomaly in the upper crust.

Accurate documentation of the location and geometry of seismogenic faults are critical for understanding strong seismicity and seismic hazard mitigation. A rising concern worldwide is induced seismicity caused by hydraulic fracturing, yet the geological characteristics and mechanisms of such seismogenic faults remain insufficiently understood. In particular, a first -order issue is whether the strong (M >= 5.0) induced earthquakes are caused directly by the slip of shallow faults near shale reservoirs or indirectly by deep basement faults. The September 16, 2021 Ms 6.0 (Mw 5.4) Luxian earthquake in the Sichuan Basin, China is one of the world's greatest induced earthquakes related to shale gas exploitation. Here we constrain the geometry of the seismogenic fault of this earthquake using three-dimensional seismic reflection data and a dense seismic array. Pre-existing faults in the sedimentary cover are clearly visible in seismic coherence slices. However, these shallow faults do not match the seismological parameters of the Luxian earthquake. High-resolution seismic reflection profiles combined with relocated earthquakes indicate that the seismogenic fault is located in the Precambrian basement. The results suggest that the mainshock is most likely caused by the poroelastic effects due to fluid injection. Hydraulic fracturing could have reactivated a large-scale basement fault and triggered the strong earthquakes under a relatively high geo -stress conditions in the study area. The basement fault slipped upward and ruptured the sedimentary cover, resulting in a significant difference between the focal and centroid depths of the mainshock. Our findings emphasize the importance of investigating regional tectonic and geological settings, local stress fields, and pre-existing faults for studying potential induced seismicity in shale gas fields.

中国地震科学实验场位于青藏高原、华南块体和印度板块的交汇地带,地质构造复杂、地壳变形强烈,是我国大陆强震最活跃的地区.高分辨率的壳幔三维速度结构是认识强震孕育环境、壳幔变形机制和深部动力学过程的重要基础.本研究基于接收函数与面波联合反演方法构建高垂向分辨率三维初始速度模型,采用双差层析成像方法获得了中国地震科学实验场最高横向分辨率为0.25°的三维P波和S波速度模型CSES-VM1.0.受Sn观测资料的限制, S波速度模型在下地壳和上地幔顶部的分辨率降低,使其更接近接联合反演给出的初始模型.基于人工爆破观测数据的检验表明,与以往的速度模型相比,新模型的初至P波理论走时更接近观测值.横跨2022年芦山6.1级地震和泸定6.8级地震震源区的速度剖面揭示,前者发生在青藏高原与四川盆地相接触的软弱带附近,后者位于花岗岩分布区,北段受强度较大的高速体阻挡.扬子板块西缘存在断续分布的显著高速异常带,揭示了新元古代中基性侵入岩的空间分布,并在很大程度上控制了断裂带的分布形态,甚至影响大地震的破裂过程;攀枝花附近存在沿北东-南西和南北向分布的两个高速异常,它们可能与新元古代和中晚二叠世的中基性侵入岩分布有关.在实验场西南地区,成像结果清晰地揭示出临沧花岗岩带、思茅盆地“中轴”断裂带隆起区以及哀牢山杂岩带的空间分布,展现出比以往成像模型更高的空间分辨能力.本项工作建立的速度模型可为地震科学实验场深部构造研究、高精度地震定位和强地面运动模拟等提供重要基础.

The interior of the Ordos block, located northeast of the Qinghai-Xizang Plateau, is not entirely stable or homogeneous and may have been subjected to tectonic deformation. However, there has been no definite conclusion regarding the extent and mechanism of this deformation. Here, we obtained a high-resolution P-wave velocity (Vp) model for the northeastern Qinghai-Xizang (Tibetan) Plateau, Ordos block and surrounding areas using traveltime data involving over 1200 stations from a newly deployed dense temporary array and permanent seismic network. Our results showed that the northern part of Ordos has a relatively high Vp with minimal lateral change. In contrast, the Vp structure in the southern Ordos block varied in the lateral direction, with low-velocity anomalies at a depth of 15 km. The lower crust with Vp from 6.8 to 7.3 km s-1 is thicker in the west and gradually thins towards the east. The northern part of the Ordos block is relatively stable, whereas the southern part has undergone crustal deformation. This deformation may be related to the eastward compressive forces from the Longxi block, which could be associated with the change in the Haiyuan fault from thrust to strike-slip. In the Bayan Har block, a thick low-velocity anomaly exists in the middle and upper crusts, whereas the lower crust is relatively thin. The crust in this area likely experienced crustal shortening and delamination. Beneath the Longxi and Alxa blocks, a low-velocity layer appears in the middle crust, which may be related to ductile shear in the crustal brittle-ductile transition zone caused by plateau expansion. The range of this low-velocity layer indicates that the influence of the plateau expansion exceeded that of the Haiyuan-Tianjingshan fault zone.

High-resolution seismic model is crucial for advancing our understandings on geological processes and enhancing seismic hazard mitigation programs. We construct a high-resolution China Seismological Reference Model (CSRM-1.0) in the top 100 km of the crust and uppermost mantle in continental China following a top-down construction process. The employed seismic constraints include P-wave polarization angle from tele-seismic event, short-period Rayleigh wave ellipticity from ambient noise, long-period Rayleigh wave ellipticity from earthquake data, receiver function, empirical Green's function from ambient noise, Rayleigh wave phase/group velocity dispersion curves from regional earthquakes, and Pn-wave travel time extracted from seismic data of 4,435 stations. CSRM-1.0 has a spatial crustal resolution of similar to 60 km beneath the north-south seismic belt and trans-North China orogen regions and similar to 120 km beneath the rest of continental China, and a spatial mantle resolution of similar to 300 km. CSRM-1.0 exhibits prominent velocity heterogeneities in the crust and uppermost mantle and an eastward thinning of the crust, geographically correlating with geological settings. CSRM-1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM-1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter-block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter-block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM-1.0 to the CSRM product center () as a backbone open-access geophysical cyberinfrastructure. High-resolution seismic imaging of the crust and uppermost mantle offers crucial insights into regional geological histories and enhances seismic and volcanic hazard mitigation programs. We construct a high-resolution China Seismological Reference Model (CSRM-1.0) of the crust and mantle beneath continental China with various types of seismic constraints extracted from seismic data recorded by 4,435 stations deployed across continental China since 1990. CSRM-1.0 has a spatial resolution of similar to 60-120 km in the crust and 300 km in the uppermost mantle. CSRM-1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution and improved model accuracy. Crustal composition inferred from CSRM-1.0 exhibits a general transition from a felsic upper crust to a mafic lower crust. Mafic rocks in the lower crust are found predominantly along inter-block boundaries and sporadically within the interiors of blocks, likely resulted from preferential inter-block intrusions of magmas related to various oceanic plate subductions and the Emeishan mantle plume. This study contributes seismic constraints and CSRM-1.0 to the CSRM product center () as a backbone open-access geophysical cyberinfrastructure. CSRM-1.0 is constructed with various seismic constraints from data of 4,435 stations using a self-consistent top-down construction process CSRM-1.0 improvements include accurate estimation of shallow seismic structure, increased spatial resolution, and enhanced model accuracy CSRM-1.0 reveals major crustal mafic rocks related to the past subductions, an Emeishan mantle plume and geological inter-block boundaries

The China Seismic Experimental Site (CSES) is located at the intersection of the Tibetan Plateau, South China Block, and Indian Plate and has complex geological settings and intense crustal deformation, making it one of the most seismically active areas in Chinese mainland. A high-resolution, three-dimensional (3D) crust-mantle velocity structure is crucial for understanding seismotectonic environments, lithospheric deformation mechanisms, and deep dynamic processes. We first constructed a high-vertical-resolution 3D initial velocity model using the joint inversion of receiver functions and surface waves and then obtained a 3D P- and S-wave velocity model (CSES-VM1.0) with the highest lateral resolution of 0.25° for the CSES using double-difference tomography. Owing to the limitations of the Sn observation data, the resolution of the S-wave velocity model in the lower crust and upper mantle was reduced, making it closer to the initial model provided by joint inversion. A comparison with explosive-source seismic data showed that the synthetic P-wave first-arrival travel times of the new model were closer to the observations than those of the previous velocity models. The velocity cross-sections across the source areas of the 2022 Lushan MS6.1 and Ludian MS6.8 earthquakes reveal that the former earthquake occurred near a weak contact zone between the Tibetan Plateau and Sichuan Basin, and the rupture of the latter earthquake occurred in a granitic area, with the northern end blocked by rigid high-velocity bodies. A clear high-velocity anomaly zone is distributed along the western margin of the Yangtze Block, revealing the spatial distribution of Neoproterozoic intermediate-basic intrusions. This high-velocity zone significantly controls the morphology of fault zones and influences the rupture processes of major earthquakes. Two northeast-southwest and north-south trending high-velocity anomalies were found near Panzhihua, potentially related to Neoproterozoic and Middle-Late Permian intermediate-basic intrusions. The imaging results revealed the spatial distribution of the Lincang granitoid batholith, the uplifted zone of the central axis fault in the Simao Basin, and the Ailaoshan complex belt in the southwestern CSES, demonstrating a higher spatial resolution compared to previous results. Our velocity model provides an essential foundation for deep structural studies, high-precision earthquake locations, and strong ground motion simulations in the CSES.

This dataset contains the stacked receiver function (time before the arrival time of the Moho-converted PmS phase) estimated from 2,125,021 original receiver functions, calculated based on the waveforms of 9361 tele-seismic events recorded by 3848 seismic stations deployed in continental China. This dataset results from a project of constructing a 3-D seismic model of the shallow crust in continental China (Xiao et al, 2021, GJI) (model link). 本数据集包含了从 2,125,021 条原始接收函数计算的单台叠加接收函数(时间早于 Moho 面 PmS 转换波到时)。原始接收函数的计算基于中国大陆区域 3848 个地震台站接收的 9361 个远震事件的波形。该数据库源于构建中国大陆区域高精度浅层地壳三维地震学模型的工作 (Xiao et al, 2021, GJI) (模型链接) 。 If you face any problem or issue in the usage of this dataset, please feel free to communicate with the corresponding author Xiao Xiao (xiaox.seis@gmail.com).

It is essential to investigate the spatial distribution of the lithosphere and asthenosphere in detail, to further obtain the understanding of the effect of plate collision and the process of orogenic movement. From the joint inversion of receiver functions and surface waves, the three-dimensional S-wave velocity structure results down to 200 km depth in the study area were obtained at 1,843 seismic stations. Analysis was performed on the sedimentary thickness, crustal thickness, lower crustal wave velocity, and lithospheric thickness. According to the crustal thickness, we evaluated the distribution of low-velocity zones in the lower crust. The results show that there are low-velocity bodies in the lower crust in the Qinling tectonic belt, but they are not connected, indicating that they may not be able to be used as a channel for material extrusion from the NE Tibetan Plateau at the crustal scale. According to the section results and the depth distribution of the lithosphere-astenosphere boundary, a relatively thick lithosphere exists below the Sichuan Basin and Ordos Basin, and the lithosphere in the east of the study area is relatively thin with a thickness of about 60–80 km, indicating that the lithosphere in the east of the study area has been severely destructed and restructured. The delamination has been observed in the lithosphere under the Songpan-Ganzi Block, showing characteristics of vertical movement of asthenosphere materials. There is a relatively thick low-velocity zone at the top of the mantle lithosphere of the NE plateau; however, it does not exist under the relatively stable Sichuan Basin and the Ordos Block. Compared with the Sichuan Basin and the Ordos Basin at both sides, the Qinling tectonic belt has a low-velocity zone at the depth of 100–160 km, which may be asthenosphere material. In combination with the polarization direction characteristics of the SKS wave, it is clearly observed that asthenospheric material movement exists in an approximate east-west direction beneath the Qinling tectonic belt. Therefore, the asthenosphere beneath the Qinling tectonic belt may serve as an important channel for material extrusion in the NE Tibetan Plateau.

This dataset contains the manually-picked 95,878 Pn travel times collected from the regional P wave waveforms recorded by 3,446 seismic stations deployed in and around continental China for a total of 6,787 seismic events between 1992 and 2020. This dataset results from a project of constructing an uppermost mantle seismic Pn-velocity in continental China (Ma et al., 2023, JGR: Solid Earth) (Model link). 本数据库包含了人工挑选的95,878个Pn 波到时,这部分到时由中国大陆及周边地区的3,446个地震台记录的区域P波波形挑选而来。该数据库源于构建中国大陆区域上地幔顶部Pn波速度模型的工作 (Ma et al., 2023, JGR: Solid Earth) (模型链接)。 If you face any problem or issue when using this dataset, please feel free to communicate with the corresponding author Jiayu Ma (majy18@mail.ustc.edu.cn or seisbird@gmail.com).

A series of parallel normal faults are distributed in the Helan Mountain-Yinchuan Basin tectonic belt,where a historical M8.0 earthquake occurred.It is rare that such a great earthquake occurs in a normal fault system within the continent.To deeply understand the fine structure of the normal fault system,we deployed 104 broadband temporary stations near the system,collected data from permanent stations and other temporary stations nearby,and obtained the high-precision threedimensional S-wave velocity structure beneath 206 stations via joint inversion of receiver function and surface wave.A typical graben-in-graben feature bounded by four major faults was identified in the Yinchuan Basin.We analyzed the seismicity in the normal fault system and found a seismic strip in the southern part of the basin,where there are significant changes in the sedimentary thickness,which is speculated to be the southern boundary of the normal fault system.There are significant differences in the crustal thickness and velocity structure in the crust on both sides of the boundary between the Helan Mountain and the Yinchuan Basin,and a low-velocity zone was identified in the upper mantle beneath this boundary,which could be related to the fact that the Helan Mountain-Yinchuan Basin tectonic belt is located between the Alxa Block and the Ordos Block.The M8.0 Yinchuan-Pingluo earthquake occurred at the junction of four major faults in the Yinchuan Basin,which was located in the high-velocity zone near the velocity transition zone at the basin-mountain boundary.The low-velocity zone in the upper mantle beneath this boundary may have promoted the nucleation of this earthquake.Based on evidence from geological drilling,micro seismicity,the regional stress field,and the velocity models obtained in this study,it is inferred that the eastern piedmont fault zone of the Helan Mountain was the seismogenic fault of the 1739 M8.0 Yinchuan-Pingluo earthquake.