The 3‐D Structural Model of an Out‐of‐Sequence Earthquake in China: Implication for the Reactivation of Positive Inversion Structures Along the Northern Tianshan Fold‐and‐Thrust Belt

Abstract

The intracontinental earthquake behavior is not well understood due to its complexity in the interior of the continent. The Tianshan Mountain is located in the interior of the Eurasian plate, which was rejuvenated in the Cenozoic due to the India‐Asia collision and sourced several large earthquakes. The 2016 Hutubi earthquake occurred within the northern Tianshan, China, during rupture of a high‐angle back‐thrust toward the hinterland, which broke the long‐time quiescence in the mountain front. The geometry, dynamics, and hazard implications of this earthquake on an out‐of‐sequence thrust fault remains unclear. The 3‐D structural model shows that the coseismic fault is connected to the large‐scale blind Southern Junggar thrust, which sourced the 1906 Mw ~8 Manas earthquake. The geometry of the coseismic fault and the occurrence of extensional tectonics in the Jurassic suggest that the Hutubi earthquake occurred on a reactivated rift‐related structure. To test this hypothesis and study the kinematics, we performed sandbox modeling, with results suggesting that coseismic fault can form during positive inversion of a preexisting Jurassic rift, and that the Southern Junggar thrust and related structures may be recently active. Coal beds facilitated the transfer of fault slip and strain from mountain to basin and from basal to roof detachment. We propose that the preexisting rift and related sedimentation controlled the subsequent structure and geomorphology of the mountain belt through thrust wedge formation. This study provides a typical example for the study of intracontinental inversion structure and its earthquake behavior.

Response of Surface Erosion to Crustal Shortening and its Influence on Tectonic Evolution in Fold‐and‐Thrust Belts: Implications From Sandbox Modeling on Tectonic Geomorphology

“…The structural deformation of F2 occurs only above the detachment layer. It has been studied that shortening can be accommodated by active‐roof, passive‐roof, or composite‐roof duplexes with the presence of shallow detachment in the foreland (Bonini, 2007; Li et al., 2018). Erosion across the wedge promotes the formation of passive‐roof duplexes (Mugnier et al., 1997).…”

“…The crustal structure of these three fold‐and‐thrust belts have been well understood by comprehensive studies including field investigation, seismic reflection profile, drilling exploration, etc. (e.g., Guan et al., 2016; He et al., 2009; Hubbard et al., 2010; Li et al., 2018). Thrust wedge connected the deep detachment in the hinterland and the shallow detachment in the basin.…”

The characteristics of active deformation and strain distribution in the eastern Tian Shan

“…In theory, slip partitioning often occurs in regions under oblique convergence, resulting in the development of contractional and strike‐slip structures (Braun & Beaumont, 1995; Cooke, Toeneboehn, & Hatch, 2020; Leever, Gabrielsen, Sokoutis, & Willingshofer, 2011; Tikoff & Teyssier, 1994; Figure 5), which can be inferred from GPS measurements and/or geological constraints (e.g. Calais et al, 2002; Kundu, Yadav, Bali, Chowdhury, & Gahalaut, 2014; Li, Wei, et al, 2018; Li, Zhang, et al, 2018; Mccaffrey et al, 2000; Murphy et al, 2014). Nevertheless, transpressional strain is generally not fully partitioned between pure strike‐slip and pure convergence, and many parameters (e.g.…”

“…Right-lateral strike-slip motions are observed at the Kaidu River Fault by previous studies (Fu et al, 2003;Huang et al, 2018;Lin et al, 2002). SRTM, Shuttle Radar Topography Mission [Colour figure can be viewed at wileyonlinelibrary.com] Kundu, Yadav, Bali, Chowdhury, & Gahalaut, 2014;Li, Wei, et al, 2018;Li, Zhang, et al, 2018;Mccaffrey et al, 2000;Murphy et al, 2014). Nevertheless, transpressional strain is generally not fully partitioned between pure strike-slip and pure convergence, and many parameters (e.g.…”

“…For instance, the Southern Junggar Thrust (SJT) hosted the 1906 M ~ 8.0 Manas earthquake with prominent surface ruptures along the Huoerguosi–Manas–Tugulu structural belt (Avouac et al, 1993; Deng, Zhang, Xu, Yang, & Peng, 1996; Stockmeyer, Shaw, & Guan, 2014). Recently, the 2016 M ~ 6.2 Hutubi earthquake has also been inferred to be associated with the SJT (Li, Wei, et al, 2018; Lu et al, 2018). In the eastern Tian Shan, besides the predominance of contractional structures, active dextral slip along the NW‐trending faults has also been demonstrated, including the Bolokelu‐Aqikekuduke (Bo‐A) Fault in the northern part (Campbell et al, 2013; Shen, Wang, Li, Jiang, & Xiang, 2003; Yang & Shen, 2000) and the Kaidu River Fault in the southern part (Fu, Lin, Kano, Maruyama, & Guo, 2003; Huang, Yang, Li, & Yang, 2018; Lin, Fu, Kano, Maruyama, & Guo, 2002).…”