新疆乌什地区构造应力场特征及乌什7.1级地震对其的影响OA

[Objective]The Wushi region in Xinjiang is located at the intersection of multiple tectonic units,characterized by frequent tectonic activity,making it a critical region for stress concentration and release.On January 23,2024,an M 7.1 earthquake struck Wushi(epicenter:41.26°N,78.63°E;depth:22 km),representing the largest event in this area over the past decade.To better understand the regional seismogenic environment and assess future seismic hazards,this study utilizes comprehensive focal mechanism data to investigate the regional tectonic stress field and quantitatively evaluate the impact of the M 7.1 Wushi earthquake on the stress regime.[Methods]Based on 148 focal mechanism solutions(January 1976 to March 2025)compiled from multiple domestic and international institutions,we applied the damped stress tensor inversion method to determine the stress field characteristics across subregions and systematically evaluate changes in the stress field before and after the earthquake.[Results]Stress tensor inversion reveals that the Wushi region is dominated by a compressional stress regime under N-S compression.Except for the area near the Jiashi earthquake cluster where R>0.5,the azimuth of the maximum principal compressive stress(σ1)gradually rotates from NNW in the south to approximately N-S in the north(azimuth range:168.75°-183.45°;plunge range:6.85°-19.58°).The Jiashi seismic cluster exhibits a strike-slip stress regime characterized by NNE-SSW compression and NWW-SEE extension,with thrust faulting dominating to its north and strike-slip faulting to its south.Comparative analysis shows that the optimal σ1 direction adjusted from an azimuth/plunge of 178.91°/6.24° before the earthquake to 167.61°/7.98° after the earthquake,corresponding to an azimuth deviation of 12.53° and a total spatial rotation of 15.06°.This indicates that the mainshock exerted a relatively minor impact on the regional stress field,which remains under the dominant compressional regime.[Conclusions]The tectonic stress field in the Wushi region is driven by the northward collision of the Indian plate against Eurasia,which transmits near-N-S horizontal compression northeastward into the Tianshan orogenic belt,causing crustal shortening and thrusting between the Tarim Basin and the Tianshan Mountains.The M 7.1 earthquake caused only localized adjustments,leaving the overall regional stress regime controlled by deep-seated tectonic processes.Furthermore,the northern Jiashi earthquake cluster,located at the boundary between the northern Tarim plate and the Tianshan Mountains,exhibits a strike-slip stress mechanism,marking a major tectonic transition zone between the Tarim Basin and the Tianshan orogenic belt.[Significance]This study provides a refined characterization of the tectonic stress field in the Wushi region and clarifies the limited impact of the M 7.1 mainshock on regional stress states.These findings deepen our understanding of the tectonic interactions between the Tianshan orogenic belt and the Tarim Basin,providing critical scientific constraints for regional tectonic segmentation and seismic hazard assessment.