Hongyi Li

The Xianshuihe fault zone (XSHF), a major strike-slip system on the southeastern Tibetan Plateau, is one of the most seismically active structures in China. However, the relationship between its kinematics and long-term seismic behavior remains poorly understood. Here, we utilize continuous seismic data from 2014 to 2022, employing machine learning to detect 12,534 events, and invert for a regional 3D velocity model. We further derive a fault locking model from Global Navigation Satellite System data and systematically analyze spatiotemporal seismicity patterns and statistical features. Results reveal pronounced segmentation in seismicity along the northern XSHF. Along with low b values and a southward shallowing of seismogenic depths, locking constraints delineate two primary zones of enhanced locking north of the Bamei region, which are embedded within a northern fault segment that remains predominantly locked as a whole. In the Bamei–Kangding segment, a releasing bend concentrates seismicity along the western and southeastern faults, with marked spatial variations in b values. Velocity and resistivity structures indicate that the extensional environment of pull-apart basins facilitates deep melt upwelling. Overall, the northern XSHF is progressively entering a locked state, with potential for Mw 6.8+ earthquakes, whereas the Kangding segment structural assemblage modulates regional compressive and strike-slip stress loading. These constraints help clarify aspects of seismic behavior and deformation in intracontinental block-margin strike-slip systems and may inform regional seismic hazard assessment.

Large intraplate earthquakes are paradoxical because they occur far from active plate boundaries. Northern Hainan Island (South China) hosts the 1605 Qiongbei M7.5 earthquake within a volcanic province linked to the Hainan mantle plume. New shear‐wave velocity images reveal two shallow low‐velocity zones extending to ∼10 km depth: a stronger anomaly beneath young volcanic cones and a weaker anomaly beneath the seismogenic fault system. Both anomalies connect near ∼6 km depth and merge into a deeper anomaly at 12–30 km depth that spatially coincides with low‐resistivity structures imaged by magnetotellurics, indicating a vertically connected crustal magmatic‐fluid system. Locally thinned crust and low uppermost‐mantle velocities further suggest ongoing plume‐fed mantle upwelling. We infer that volatile‐rich fluids ascended into shallow fault zones, reducing rock strength and promoting rupture during the 1605 earthquake. These results link mantle upwelling to brittle fault failure and suggest that plume‐derived magmatic fluids may govern large intraplate earthquakes.

On 23 January 2024, an MS 7.1 earthquake struck the Maidan fault (MDF) near Wushi County, China, located at the junction of the southern Tianshan and Tarim Basin, the largest recorded earthquake on this fault within the past century. To date, the detailed fault structure remains poorly understood due to sparse station coverage. We applied machine learning–based techniques to construct a high-precision earthquake catalog for the Wushi earthquake sequence, covering the period from 13 January 2024 to 1 March 2024. The resulting catalog comprises 17,021 earthquakes; ~2.4× the size of the routine catalog reported by the China Earthquake Networks Center (CENC; https://www.cenc.ac.cn/). We further determine focal mechanisms for 33 events (ML ≥ 2.55) using waveform-based inversion methods, revealing that ~75% of earthquakes exhibit reverse faulting characteristics. Stress field inversion based on these focal mechanisms indicates a regional stress regime of nearly horizontal north-south convergence and vertical extension. Spatial and kinematic analysis of the aftershock sequence reveals a complex fault system, composed of multiple secondary reverse and strike-slip faults with varying geometries, that is situated within the transitional zone between the MDF and the Wushi Basin and includes two southward-dipping imbricate fan structures that likely form a triangular zone with the northward-dipping main MDF. Our observations highlight the geometric complexity of the fault system in this region and its coordinated geomechanical expression of regional strain accumulation and release.

Due to the collision between the Indian and Eurasian plates and the southeastward compression of the Tibetan Plateau, western Yunnan is one of the regions in China with the most active seismic and volcanic activities as well as the most complex fault structures. We first built a deep-learning-based high-precision earthquake catalog for the Tengchong volcanic field over the past decade and found that 1) ∼59% of the seismicity occurred as swarms but on faults aligned with the regional tectonic stress field; 2) all swarms contained fluid-diffusion-like migration fronts; and 3) a year-long swarm, including two ML 5.2 earthquakes within two months, revealed complex fluid-fault interaction. Combined with the historical occurrences of M >6 earthquake swarms around the Tengchong volcanic field, our observations suggest potential increased likelihood of swarms with large-magnitude earthquakes where large tectonic faults and magmatic systems intersect.With the aid of machine-learning-based detection, we then outlined a complex 3D fault zone accommodating a small earthquake swarm near Yunlong city, western Yunnan, China from February to May 2013. Our results showed that the swarm initiated from a compressive stepover zone and subsequently activated a complex fault zone including six planar fault segments. The migration front of the swarm can be well-modeled by fluid diffusion, indicating the swarm was primarily driven by pressurized fluid. Within the stepover zone, complex and dense fractures act as conduits connecting the reservoir and fault zone, facilitating fluid flow. Meanwhile, the stress in the stepover zone tends to increase in response to the compression of the two boundary faults, which not only makes the stepover zone more susceptible to be triggered by those transient stresses but also forms a fluid pumping mechanism that drives fluids from the stepover zone into the complex fault zone.By integrating a deep-learning-based phase picker and an improved match-and-locate algorithm, we constructed a high -precision foreshock catalogue for the 2021 Yangbi earthquake. Meanwhile, a high-resolution earthquake source region velocity structure for the 2021 Yangbi sequence was also inverted in our study. Our results suggest that natural fluid diffusion is likely a driver of the Yangbi foreshock sequence based on three lines of evidence: 1) regions with low Vs and relatively high Vp/Vs are widespread within the fault system; 2) earliest foreshocks exhibit diffusion-like migration front, and 3) foreshock evolution coincides with typical fault valving behavior, and a few low-frequency signals whose distribution coincides with high Vp/Vs patches was clearly identified, strongly suggesting that fluid diffusion influenced nucleation.Therefore, we propose that the interaction between the widely distributed fluids and faults in western Yunnan may play a crucial role in the seismic activity.

Within the collision zone between the Arabian and Eurasian plates, the Anatolian Plateau represents an early stage in the closure of the Neo-Tethys Ocean (Teknik et al., 2025). The uplift mechanism of the Anatolian Plateau remains debated, as the primary geodynamic drivers likely vary regionally. While upper-crustal shortening dominates the northern margin of Central Anatolia, slab break-off and mantle upwelling are key along the southern and interior margins (Şengör et al., 2008; Yildirim et al., 2011). These processes are not isolated but may be geodynamically linked through subsequent shifts in plate motion and mantle flow following slab break-off. The Pn wave is a seismic phase that propagates primarily within the uppermost mantle. Its attenuation characteristics serve as a proxy for physical properties such as temperature, pressure, and water content in this region. Therefore, high-resolution attenuation tomography of the uppermost mantle using Pn waves can provide key constraints on the tectonic evolution of the Anatolian Plateau. In this study, we collected 23,830 seismic waveform data from 853 events recorded by 717 seismic stations between July 1996 and August 2025. Using a joint inversion method (Zhao et al., 2015), we constructed a broadband (0.05 - 20.0 Hz) high-resolution (1.0 1.0) Pn-wave attenuation model for the Anatolian Plateau. A prominent high-Q region observed in the southwestern part of the study area represents the Aegean Slab while a localized high-Q zone surrounded by low-Q anomalies (at approximately 36°E, 39°N) correlates with volcanism in the Central Anatolian Plateau. This work was supported by the National Natural Science Foundation of China (No. 42430306).

The convergence of the Indian and Eurasian plates beneath the Pamir Plateau has produced complex continental subduction, significantly influencing upper crustal faulting and seismicity. To investigate the kinematic behavior of the High Pamir Plateau, we derive a geodetic slip model for the 2023 Mw 6.9 Pamir earthquake by using Sentinel‐1A and ALOS‐2 InSAR data. Our geodetic inversion reveals rupture along two distinct faults: a dominant left‐lateral strike‐slip fault and a secondary normal fault, consistent with the mechanisms of the 1911 Mw 7.3 and 2015 Mw 7.2 earthquakes in the region. Notably, the 2015 and 2023 ruptures extend to ∼20 km depth—deeper than typical Tibetan Plateau earthquakes—likely due to the thermal influence of the underlying cratonic lithosphere. Our results also indicate a broad shear zone above the underthrusting Indian plate, underscoring the role of lithospheric‐scale dynamics in shaping crustal fault behavior in the Pamir region.

The Longmen Shan (LMS) fault zone, located in the eastern margin of the Tibetan Plateau, serves as the principal fault controlling the regional seismicity. Because of the harsh natural environment, previous studies in this region have primarily focused on large-scale crustal and mantle structures, with limited attention to shallow, near-surface features. However, fine structures of the northern LMS central fault zone (Guangyuan area) remain unclear. To investigate the near-surface characteristics, we used ambient noise data recorded by 54 short-period three-component seismometers deployed across the northern LMS fault zone, between 16 March and 6 April 2023, based on surface-wave attenuation tomography and horizontal-to-vertical spectral ratio (HVSR) methods. Surface-wave attenuation measurements reveal a low Q-value in the LMS central fault zone, characterized by widespread attenuation and significant heterogeneity. Differences between Rayleigh- and Love-wave attenuation allow us to depict an imbricate thrust fault plane, on the hanging wall of the fault. The HVSR results show conspicuous variation in resonant frequency and amplitude data at stations above the fault zone, with a correspondingly high seismic vulnerability index (K-value). By integrating the attenuation and HVSR findings, we infer that the LMS central fault zone exhibits severe near-surface fractures with a widespread distribution. In addition, the nearby Pai-lung River water may be infiltrating deeper strata through these fractures, potentially changing site stability. Understanding these fault-zone characteristics is crucial for regional development, construction, as well as seismic hazard preparation and mitigation.

The Mw 7.0 Dingri earthquake, which occurred on 7 January 2025, occurred at the southern end of the Xainza-Dinggyê Fault Zone within the South Tibet Rift (STR) system, in the Dengmecuo graben. It is the largest normal-faulting event in the region recorded by modern instruments. Using Sentinel-1A and Lutan SAR data combined with strong-motion records, we derived the coseismic surface deformation and slip distribution. InSAR interferograms and displacement vectors confirm a typical normal-faulting pattern. The slip model, based on an elastic half-space assumption, identifies the Dengmecuo Fault as the source fault, with an average strike of ~187° and a dip of ~55°. The rupture was concentrated within the upper 10 km, with a maximum slip of 4–5 m at ~5 km depth, extending to the surface with ~3 m vertical displacement. Partial rupture (≤2 m) in the southern segment (5–10 km depth) did not reach the surface, likely due to lacustrine deposits or possible post-seismic stress release. The rupture bottom intersects the fault plane of the South Tibet Detachment System (STDS), suggesting a restraining effect on coseismic rupture propagation. Considering stress transfer along the Main Himalayan Thrust (MHT), we propose that the 2025 Dingri earthquake is closely associated with stress transfer following the 2015 Gorkha earthquake in the lower Himalayas.

On 5 September 2022, the moment magnitude (Mw) 6.7 Luding earthquake struck in the Xianshuihe Fault system on the eastern edge of the Tibet Plateau, illuminating the seismic gap in the Moxi segment. The fault system geometry and rupture process of this earthquake are relatively complex. To better understand the underlying driving mechanisms, this study first uses the Interferometric Synthetic Aperture Radar (InSAR) technique to obtain static surface displacements, which are then combined with Global Positioning System (GPS) data to invert the coseismic slip distribution. A machine learning approach is applied to extract a high-quality aftershock catalog from the original seismic waveform data, enabling the analysis of the spatiotemporal characteristics of aftershock activity. The catalog is subsequently used for fault fitting to determine a reliable fault geometry. The coseismic slip is dominated by left-lateral strike-slip motion, distributed within a depth range of 0–15 km, with a maximum fault slip > 2 m. The relocated catalog contains 15,571 events. Aftershock activity is divided into four main seismic clusters, with two smaller clusters located to the north and south and four interval zones in between. The geometry of the five faults is fitted, revealing the complexity of the Xianshuihe Fault system. Additionally, the Luding earthquake did not fully rupture the Moxi segment. The unruptured areas to the north of the mainshock, as well as regions to the south near the Anninghe Fault, pose a potential seismic hazard.