The Mw 7.1 Tingri earthquake represents the largest normal-faulting event within the Lhasa block since 1952. This rupture occurred along the approximately north-southtrending Dengmocuo rift, which constitutes the seismogenic fault. The event provides an exceptional case study to examine aftershock distribution patterns and triggering mechanisms following large normal-fault earthquakes in the Tibetan plateau. We calculated Coulomb failure stress changes (Delta CFS) induced by coseismic slip and postseismic poroelastic rebound using a coseismic slip model inverted from Interferometric Synthetic Aperture Radar and strong-motion records. The earthquake rupture propagated similar to 40 km north of the mainshock hypocenter, with slip predominantly confined to the upper 10 km of the crust. Such ruptures typically produce stress loading at the fault's northern and southern termini while generating stress-shadow zones along the eastern and western flanks. Within this pattern, the main rupture zone spatially coincides with the stress-shadow zone, whereas adjacent regions constitute CFS loading zones. Postseismic fluid migration induces significant CFS loading within the main rupture zone, effectively compensating for coseismic stress shadows and subsequently triggering peripheral aftershocks. The triggering mechanisms of aftershocks vary significantly across different segments of the fault system. Coseismic slip accounts for only 44% of total aftershock triggering, whereas poroelastic rebound contributes a notably higher proportion, reaching up to 65%, particularly in the northern segment, where it peaks at 74%. This indicates that postseismic fluid migration has a significant impact on the occurrence of aftershocks in the main rupture zone.

According to the China Earthquake Networks Center (CENC), an MS6.8 earthquake occurred in Dingri County, Tibet Autonomous Region, China, on January 7, 2025, with a focal depth of 10 km. The epicenter was located in the southern part of the Tibetan Plateau. Due to the northward push of the Indian Plate, a series of north-south trending rifts have formed within the block containing the epicenter. The seismogenic fault is identified as the Dengmocuo Fault in the southern segment of the Shenzha-Dinggye Rift. Within one week after the mainshock, 55 earthquakes of MS≥3.0 were recorded, including one aftershock of MS≥5.0—an MS 5.0 event on January 13th. Focal mechanism solutions from different institutions consistently indicate that the mainshock was an extensional rupture event with a nearly north-south striking plane, essentially consistent with the trend of the Shenzha-Dinggye Rift. Based on the CENC catalog, earthquakes of ML≥3.0 within the aftershock zone are overall distributed along a north-south orientation. The epicentral distribution map shows that, bounded by latitudes 28.8°N and 28.6°N, the aftershock zone can be divided into three main areas: northern, central, and southern. The mainshock is located in the southern area. ML≥3.0 aftershocks are primarily distributed in the northern and southern areas, with fewer and more scattered events in the central area.We collected waveform data for earthquakes of M≥3.0 within the aftershock zone from January 7 to 14. After quality screening, we determined the focal mechanism solutions for moderate and small earthquakes based on P-wave first motions, obtaining solutions for a total of 30 events. The results show that the focal mechanisms in the northern and central areas are predominantly strike-slip, although the number of solutions from the central area is limited. The focal mechanisms in the southern area are relatively complex, mainly characterized by extension with a subordinate strike-slip component. Subsequently, we inverted the regional stress field. Given that the aftershocks are basically aligned north-south with a narrow east-west distribution, we calculated the stress field from south to north at intervals of 0.2 degrees using a radius of 20 km. The calculation results show that the orientation of the maximum principal compressive stress (σ1) within the aftershock zone is essentially north-south, indicating that the overall rupture is dominated by east-west extension. Furthermore, the R-values from north to south are 0.8, 0.5, 0.1, and 0.2, respectively. This reveals a gradational stress pattern across the entire aftershock zone: "strong compression in the north → weak planar stress in the central area → weak compression in the south," with no abrupt changes. This suggests that the post-mainshock stress adjustment is continuous and controlled by the regional tectonic setting, with no significant stress discontinuity. A transition in the stress state from compression in the north to extension in the south is observed.

In this study, we collect seismic P-and S-wave travel time data from January 1, 2015 to January 22, 2025, recorded by the permanent and temporary stations in the area surrounding the Dingri MS6.8 earthquake to invert 3D fine P-wave and S-wave velocity structures above a depth of 30 km and relocate seismic events by applying the double-difference tomography method. The results show that the relocated aftershocks delineate an approximately 80 km-long, nearly north-south-trending belt on the western side of the Dengmecuo Fault, exhibiting clear along-strike segmentation: the northern segment (north of 28.8 degrees N), the central segment (28.6 degrees N-28.8 degrees N), and the southern segment (south of 28.6 degrees N). The central segment contains multiple branch faults that strike, from west to east, NNW, nearly NS, and NNE, respectively, while the southern segment exhibits an overall NNW orientation. The mainshock is located at the intersection of the nearly east-westtrending South Tibetan Detachment System and the north-south-striking Dengmecuo Fault in the southern segment, with a focal depth of 11.6 km. The aftershocks are concentrated at depths between 4 and 20 km and shallow northward along the northern segment. The velocity structure in the source region shows pronounced lateral heterogeneity: the western part is generally characterized by low-velocity anomalies, whereas the mainshock and most aftershocks are located in a velocity transition zone biased toward the high-velocity domain, with a pronounced low V-P/V-S anomaly observed around the mainshock. Comprehensive analysis suggests that during the steep-angle subduction of the Indian slab beneath the Tibetan Plateau, slab tearing enabled deep hot material to ascend through the tear window or via vertical mantle flow into the mid-lower crust, thereby generating a stress concentration zone in the mid-upper crust. Against the background of ongoing accumulation of regional east-west extensional tectonic stress, the interaction of multiple intersecting faults ultimately triggered the Dingri M-S 6.8 earthquake.

Foreshocks play a crucial role in providing insights into the earthquake nucleation process. Analyzing the foreshock characteristics of typical earthquake cases is essential for enhancing our understanding of the mechanisms behind earthquake nucleation. Although most case studies focus on earthquakes with significant foreshocks, studies of earthquakes with less obvious or initially undetected foreshocks can broaden our perspective on the earthquake nucleation process. The 2014 Ms 6.5 Ludian earthquake is a typical intraplate earthquake that was initially cataloged without obvious foreshocks. In this study, we first used the hypoDD method to accurately relocate earthquakes near the Ms 6.5 Ludian earthquake and then applied the match-and-locate method to detect and locate missing events from 65 days before to 29 days after the mainshock. The updated catalog included 4285 seismic events, nearly doubling the original catalog. The number of foreshocks increased from 19 to 155, with magnitudes ranging from ML-0.3 to 2.7. We found that the b value of the foreshock sequence is significantly higher than that of the aftershocks, which is likely due to differences in the fault segments associated with the foreshock and aftershock activity zones, as well as the incomplete release of stress along the fault during the mainshock. The spatiotemporal evolution of the foreshocks revealed a migration trend toward the mainshock, followed by a period of quiescence. Observations of migrating foreshocks and repeating earthquakes indicate that aseismic slip plays an important role in the initial nucleation process. Considering existing research on earthquake rupture processes and Global Positioning System observations, we suggest that cascading stress transfer also contributes to the nucleation process. Therefore, we propose that multiple mechanisms can work together, and the rate-dependent cascade-up model better explains the nucleation process of the Ludian earthquake.

The 2021 Maduo MS7.4 earthquake occurred in the Jiangcuo fault with left-lateral strike-slip movement. In order to study the movement and deformation characteristics of the Jiangcuo fault before the Maduo earthquake and further analyze the seismogenesis process of the continental strong earthquake, the large-scale strain rate field distribution in western China, the locking degree and the evolution of slip deficit rate of the Jiangcuo fault, and the rupture mechanism of seismogenic fault are analyzed and discussed in this paper using the GPS velocity field on a long time scale and InSAR dynamic velocity field. The results show that: (1) The strain rate field in EW direction shows that the Maduo earthquake is located at the edge of the EW direction strong compression zone of Bayanhar block. The eastern part of the Maduo earthquake is a compression strain accumulation zone, and the western part is a gradual transition from weak compression to tension strain. The results of the maximum shear strain rate field show that the Maduo earthquake is located at the edge and high gradient zone of the high value area of the maximum shear strain rate field. (2) The inversion results of the locking degree show that deep unlocking occurs in some regions in the east and west of the epicenter of the fault during 2015-2021, gradually transitioned to a completely locked state in the middle of the fault, and the focal point of Maduo earthquake is at the edge of the completely locked region in the transition region. The dynamic results from 2015 to 2017 and 2017 to 2019 were basically stable. The whole fracture plane was basically in a state of strong locking, and only partial unlocking with a depth below 15km existed in local areas. From 2019 to 2021, some faults in the east and west of the epicenter have deep and shallow unlocking phenomena, including the overall unlocking of most areas of the western section and the local deep unlocking of the East section of the ruptured fault, while the rapid unlocking of the two sides of the epicenter may contribute to the occurrence of the main earthquake. This work was supported by Science for earthquake resilience (XH23047A).

The discrimination of natural and unnatural seismic events is an important part of earthquake monitoring and early warning. Deep learning algorithms, with their powerful feature extraction and classification capabilities, are extensively applied in seismic event identification. In this study, we utilized the DiTing 2.0 dataset to develop binary-class networks for distinguishing low-magnitude earthquakes from explosions, as well as three-class networks for identifying low-magnitude earthquakes, explosions, and collapses. The accuracies achieved for discriminating earthquakes from explosions using waveform and spectrogram datasets are 94% and 87%, respectively. The accuracies for discriminating earthquakes, explosions, and collapses using waveform and spectrogram datasets are 85% and 83%, respectively. We then apply the trained three-class model to discriminate explosions and collapses in four different regions in China. The prediction results indicate that the trained model can accurately identify event types and exhibits a good performance in low-magnitude seismic event (M-L < 5) discrimination, demonstrating the effectiveness and generality of the models developed in this study.

Soils contain a diversity of microbial communities involved in the nitrogen cycle (N-cycling), which are essential for maintaining the quality and health of soil. However, agricultural intensification has led to land use conversion, which has had a negative impact on ecosystems. There is a lack of research on the whole N-cycling process in land use change under the context of ecological restoration. Here, we utilized qPCR (Quantitative Real-time PCR) and MiSeq techniques to analyse the functional genes related to nitrogen fixation (nifH), nitrification (AOA and AOB) and denitrification (norB and nosZ) to explore whether the conversion of farmland to forest and grassland affects changes in microbial communities involved in the N-cycling. We reveal the potential effects of ecological restoration on microbial community function in the N-cycling through soil properties. Specifically, land use conversion increased N-cycling gene abundance and changed in the N-cycling microbiome exhibited. The ecological restoration has increased the importance of stochastic processes in the assembly of AOA and AOB communities and affected the ecological cluster of soil N-cycling microbial network. Overall, these findings reveal specific microbial processes and interactions that influence the soil N-cycling and provide insights for future research on sustainable land management approaches that support soil health.

Based on the literatures in the field of earthquake disaster research in China in the past 20 years (2003—2022) collected by China Knowledge Network, this article studied the overall distribution, research hotspots and frontier evolution trajectory of earthquake disaster research using the scientometric software CiteSpace. The results show that in the past 20 years, there has been a limited number of literatures on earthquake disaster research, which is closely related to earthquake events. Research institutions mainly focus on functional departments responsible for earthquake work, and the main research hotspots are focused on obtaining disaster data and extracting disaster information. After analysis, the evolution trajectory of earthquake disaster research can be divided into the initial stage, development stage, and deepening stage. The current research hotspots mainly focuses on the acquisition of disaster data, which is in the early stage of earthquake disaster research and an important stage of laying a solid foundation. In the future, the research on earthquake disasters in China should strengthen the integration of disciplines, pay attention to expanding the research direction of disaster information extraction, disaster reporting and release, and realize the intelligence, dynamics and three-dimensional of earthquake disasters by combining mainstream technologies.

Although the Qilian-Haiyuan fault is known to be responsible for major earthquakes up to M 8, the potential of damaging earthquakes near its western end is not well under-stood. Since January 2022, three moderate earthquakes (M 5.8, M 6.0, and M 5.4) occurred around the Halahu region of Delingha, China, near the western end of the Qilian-Haiyuan fault. These earthquakes are unusual M 5+ events in this low-seismicity region, and both the U.S. Geological Survey and Global Centroid Moment Tensor solutions suggest that the focal mechanisms of the three mainshocks are distinct from the activity characteristics of the nearby mapped faults. Thus, determining the precise source parameters and identi-fying the causative fault of this earthquake sequence are important to analyze its seis-mogenic settings and seismic hazard in this region. In this article, we determined the point-source parameters of the three moderate events via regional waveform modeling and found that these earthquakes are strike-slip events with the nodal planes striking nearly north-south and east-west directions. We then resolved its seismogenic faults by analyzing the aftershock distribution and the rupture directivity. The results show that both the M 5.8 and M 6.0 events ruptured along the north-south nodal plane and expanded toward the south for -4 km and -3 km, respectively, and the ruptured fault of the M 5.4 is difficult to distinguish. Furthermore, we constrained the relative location using the Interferometric Synthetic Aperture Radar observation, and the result is consis-tent with that obtained from seismic waveform data. We proposed that this earthquake sequence ruptured along an unmapped dextral fault, which forms a conjugate fault sys-tem with the sinistral strike-slip Qilian-Haiyuan fault. Its deformation mechanism may be controlled by long-term, protracted, nearly north-south-trending, right-lateral simple shear in the Qilian Shan fold-thrust belt. The accumulated static Coulomb stress changes resulted in the northwest of this ruptured fault being closer to failure in the future.

The hydrochemistry composition and circulation path, and tectonic geothermal characteristics of hot springs are one of the effective methods to analyze the fluid coupling mechanism in active fractures and to discuss the effects of fluid on earthquakes. This paper estimates the geothermal reservoir temperature using the silicon-enthalpy model. Exposed temperature, hydrochemistry composition, geothermal reservoir tepmperature, circulation depth, and isotope composition (delta D and delta O-18) of hot springs are analyzed in several active faults in northwest Yunnan. The precise relocation of earthquakes in the study area is conducted, and the relationship between earthquakes' focal depth and hot springs' geothermal reservoir temperatures is considered. The b-value is calculated, and the correlation between shallow geothermal characteristics and seismic activity in the region is discussed. The Yangbi M6. 4 earthquake on May 21, 2021, occurred in the transitional geothermal gradient zone (from a high value to a low value) of the shallow geothermal field.

In this article,we review the general characteristics of seismicity in and around China and the overall statistics of earthquake damage in 2021,focusing on several significant events and related scientific topics.Among them,the largest event is the MS7.4 Madoi earthquake in Qinghai Province,northwest China.The event marks another MS≥7 earthquake occurring near the boundary of the Bayan Har Block that has ended a remarkable quiescence of the MS≥7 earthquakes within the Chinese mainland.In addition,the MS6.4 Yangbi earthquake in Yunnan Province,southwest China draws the most attention because of its abundant foreshocks,which are well recorded by the densely distributed seismic stations in the surrounding regions.Regarding this event,we review several recent publications focusing on the Gutenberg-Richter b-value change and the physical mechanism of foreshocks associated with this sequence.The MS6.0 Luxian earthquake in Sichuan Province,southwest China has caused serious damage with a relatively low magnitude,partly because the focal depth of the mainshock is relatively shallow （3.5 km）.It is another strong earthquake occurring within the southeast Sichuan basin with low historical seismicity yet has increased significantly since 2015,probably due to shale gas development and associated hydraulic fracturing.

The MS6.9 Menyuan earthquake in Qinghai Province,west China is the largest earthquake by far in 2022. The earthquake occurs in a tectonically active region,with a background b-value of 0.87 within 100 km of the epicenter that we derived from the unified catalog produced by China Earthquake Networks Center since late2008. Field surveys have revealed surface ruptures extending 22 km along strike,with a maximum ground displacement of 2.1 m. We construct a finite fault model with constraints from In SAR observations,which showed multiple fault segments during the Menyuan earthquake. The major slip asperity is confined within 10 km at depth,with the maximum slip of 3.5 m. Near real-time back-projection results of coseismic radiation indicate a northwest propagating rupture that lasted for ～10 s. Intensity estimates from the back-projection results show up to a Mercalli scale of IX near the ruptured area,consistent with instrumental measurements and the observations from the field surveys. Aftershock locations（up to January 21,2022） exhibit two segments,extending to ～20 km in depth. The largest one reaches MS5.3,locating near the eastern end of the aftershock zone. Although the location and the approximate magnitude of the mainshock had been indicated by previous studies based on paleoearthquake records and seismic gap,as well as estimated stressing rate on faults,significant surfacebreaching rupture leads to severe damage of the high-speed railway system,which poses a challenge in accurately assessing earthquake hazards and risks,and thus demands further investigations of the rupture behaviors for crustal earthquakes.

The South China block has been one of the most seismically quiescent regions in China, and the geometries and activities of the Quaternary faults have remained less studied due to the limited outcrops. Thus, source parameters of small-to-moderate earthquakes are important to help reveal the location, geometry distribution, and mechanical properties of the subsurface faults and thus improve the seismic risk assessment. On 12 October 2019, two earthquakes (the Ms 4.2 foreshock and the Ms 5.2 mainshock) occurred within 2 s and are located in southern South China block, near the junction region of the large-scale northeast-trending fault zones and the less continuous northwest-trending fault zones. We determined the point-source parameters of the two events via P-wave polarity analysis and regional waveform modeling, and the resolved focal mechanisms are significantly different with the minimum 3D rotation angle of 52°. We then resolved the rupture directivity of the two events by analyzing the azimuth variation of the source time duration and found the Ms 4.2 foreshock ruptured toward north-northwest for ∼1.0 km, and the Ms 5.2 mainshock ruptured toward east-southeast (ESE) for ∼1.5 km, implying conjugate strike-slip faulting. The conjugate causative faults have not been mapped on the regional geological map, and we infer that the two faults may be associated with the northwest-trending Bama-Bobai fault zone (the Shiwo section). These active faults are optimally oriented in the present-day stress field (northwest-southeast) and thus may now be potentially accumulating elastic strain to be released in a future large earthquake.

On May 21, 2021, two earthquakes, with magnitudes of 5.6 and 6.4 respectively, struck the Yangbi County in Yunnan, China. The epicenters of the two earthquakes were about 7 km apart, and both were located in the western Yunnan region. This region is located in the southeastern margin of the Qinghai-Tibet Plateau and the southern segment of the north-south seismic belt. Preliminary analysis shows the Yangbi M(S)6.4 earthquake sequence is with foreshock-mainshock-aftershock type, and the M(S)5.6 earthquake is the foreshock of the M(S)6.4 earthquake. In this study, using the seismic phase report provided by Yunnan Earthquake Networks, we relocated the early events (with local magnitude ML larger than 0.0 from May 18 to 25, 2021) of the M(S)6.4 Yangbi earthquake sequence using the double-difference relocation method. Meanwhile, the focal mechanism solutions and centroid depths of 31 M-S >= 3.0 events in the sequence were determined using the Cut-And-Paste (CAP) waveform inversion method. The seismogenic structure of the earthquake sequence based on the inverted results is also discussed. The results indicate: (1) The relocated 2159 M-L >= 0.0 events are distributed in a narrow zone with a length of similar to 25 km in the NW-SE direction, and a width of 5 similar to 10 km. The focal depth of the main shock is 8.9 km, and the depth range of the sequence is between 4 and 10 km with an average depth of 7.5 km. (2) The foreshock sequence shows the rupture starts from the middle, then goes to NW and finally to the SE direction. The epicenter of the main shock is located in the NW end of the aftershock region, and the epicenter of the largest aftershock (M(S)5.2 earthquake) is located in the SE end of the region. (3) The centroid depths of all the 31 events with M-S >= 3.0 from CAP method range from 4 to 11 km with a mean value of around 6.5 km, which is consistent with the predominant focal depth of the whole sequence from double-difference method. The agreement of the results of the two methods verify that the double-difference relocation result is reliable. (4) The focal mechanism solutions of the 31 M-S >= 3.0 events are mostly of strike-slip type, while some events show an obvious normal-fault component. The inverted stress result based on the focal mechanism solution is consistent with the regional horizontal principal compressional stress field, which indicates that the tectonic activity in this region is mainly controlled by the regional tectonic stress field. According to the distribution of relocated earthquake sequence, combined with the focal mechanism solutions and the regional structures, we conclude that the seismogenic structure for the Yangbi M(S)6.4 earthquake sequence is a secondary fault of the Weixi-Qiaohou-Weishan fault system.