Active Structural Geometries and Their Correlation With Moderate (M 5.5-7.0) Earthquakes in the Jiashi-Keping Region, Tian Shan Southwestern Front

In the tectonic framework of the seismically active Tian Shan, the Jiashi-Keping region, located at the mountain's southwestern front, is characterized by frequent moderate (M 5.5-7.0) earthquakes, rather than by strong (M >= 7.5) earthquakes as observed in other Tian Shan regions. What structures are responsible for these moderate earthquakes and whether or not more destructive earthquakes can occur remain largely unexplored. Based on an integrated analysis of published geologic and geomorphic mapping data, Google Earth satellite images, published and our collected 2D petroleum seismic-reflection profiles, as well as available seismologic data and InSAR observations, in this study, we investigate active structural geometries and their correlation with the 2020 M-w 6.0, the 2003 M-w 6.2, and other recorded major earthquakes. Our study indicates that active structures in the region can be grouped into the Kepintagh thrust imbricates, the Bachu-Kepintagh transpressional fault system, and the Xiasuhong transtensional fault system. The recorded major earthquakes are correlated with the Kepintagh thrust imbricates and the Xiasuhong fault system, both of which are highly segmented along strike and have limited downdip extensions. Although the recorded seismicity is characterized by moderate earthquakes, larger earthquakes may be generated by (i) the Bachu transpressional fault system (M-w >= 7.3) and the Kepintagh lower ramp (M-w > 7.5). Our study highlights the control of fault geometry on the seismic rupture process and regional seismic activities and enhances our understanding of seismic hazards in the Tian Shan.

Automated summary

In the seismically active Tian Shan, the Jiashi-Keping region is known for frequent moderate earthquakes and the study investigates the active structural geometries responsible for these earthquakes. Different fault systems are identified to be correlated with recorded major earthquakes, with potential for larger earthquakes to be generated by specific fault systems. The study emphasizes the importance of fault geometry in controlling seismic activities and enhancing understanding of seismic hazards in the Tian Shan region.