Present-Day Segmented Kinematic Characteristics of the Keping Nappe System, Tian Shan, Inferred from Intensive GPS Observations

Abstract The M 7.1 Wushi earthquake unexpectedly struck the eastern tail of the Keping nappe system (KNS) in the southwest Tianshan Mountains, highlighting the complex tectonic activities in this region. Traditionally, this area has only experienced moderate earthquakes with a notable scarcity of large earthquakes. The Maidan fault, the seismogenic fault, is situated within a region characterized by intense stress, yet it exhibits an exceptionally low long-term slip rate. The aim of this study is to elucidate the previously underestimated seismic risk by analyzing the strain accumulation processes of seismogenic faults and their influence on fault activities. The latest Global Positioning System data prior to the Wushi earthquake have been utilized to construct a rational block model. The results reveal that the western part of the KNS absorbs most of the crustal deformation at its southern boundary, whereas crustal deformation in the corresponding eastern part is primarily concentrated along the northern boundary. The Piqiang fault acts as a passive, inheritable tectonic boundary bisecting the KNS and accommodating differential block rotation. The Wushi earthquake may have been facilitated by slip deficits on key active faults, emphasizing the importance of understanding regional tectonics for assessing seismic risks and providing insights into the unbalanced dynamic processes shaping the KNS.