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

Abstract

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 Mw 6.0, the 2003 Mw 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 (Mw ≥ 7.3) and the Kepintagh lower ramp (Mw > 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.

Present‐Day Strike‐Slip Faulting and Thrusting of the Kepingtage Fold‐and‐Thrust Belt in Southern Tianshan: Constraints From GPS Observations

“…(2021), and Lü et al. (2021), and our interpretations) in the Jiashi‐Kepingtage and adjacent areas (location shown in Figure 1a). The P1–P11 blue dotted lines represent the GPS profile locations (see Supporting Information ).…”

“…These faults are considered to have been inactive since the Late Pleistocene and belong to the Quaternary (C. Z. Jia, 1997;Lü et al, 2021;Qu et al, 2003;Xiao et al, 2002).…”

“…The Bachu–Kepintage fault system (BKFS) includes the Bachu fault system (SSE‐trending transformations or strike‐slip tear faults) in the Tarim Basin and a NNW‐ trending strike‐slip fault or tear fault in the Kepintage FTB, which is perpendicular or oblique to the Kepintage FTB (Figure 1b, Tunner et al., 2010; Lü et al., 2021).…”

“…However, P7 reveals that the left‐lateral strike‐slip rates of the DBF and YJF are 1.10 ± 0.30 and 0.90 ± 0.26 mm/a, respectively (Figure 3a). These faults are considered to have been inactive since the Late Pleistocene and belong to the Quaternary (C. Z. Jia, 1997; Lü et al., 2021; Qu et al., 2003; Xiao et al., 2002).…”

“…The growth of orogenic belts influences the deformation rates in foreland basins, as the uplift and folding migrates from orogenic belts to the foreland (Butler et al., 2006; Lujan et al., 2003; Turner et al., 2010). Owing to the complex tectonic history and various tectonic styles of foreland basins, they are primarily manifested as folds, faults, or a combination of both (Allen et al., 1999; Heermance et al., 2008; Lü et al., 2021; McKnight, 1993; Yin et al., 1998). If the amount of shortening varies along strike, transition zones may be developed to accommodate this change in the form of strike‐slip or tear faults (Turner et al., 2010).…”