The effect of overburden thickness on deformation mechanisms in the Keping fold-thrust belt, southwestern Chinese Tian Shan Mountains: Insights from analogue modeling

The 2020 M6.4 Jiashi Earthquake: An Event that Occurred Under the Décollement on the Kaping Fold-and-Thrust Belt in the Southwestern Tien Shan Mountains, China

“…The Kashi-Aksu fold-thrust system is thought to be a thickskinned thrust on the whole (Li et al, 2012;Li et al, 2016;Borderie et al, 2018). In contrast, the Kaping fold-and-thrust belt, which is convex toward the south and overlaps the Tarim craton (Zhang et al, 2019;Li et al, 2020), is regarded as a fold-and-thrust belt. It can propagate deformation along a décollement made of a nearly 200-400 m-thick gypsiferous mudstone (Allen et al, 1999;Turner et al, 2011).…”

“…The blue circles, the purple circles, and the pink circles represent the relocated epicenters of the 1998 M6.1 and M6.4 Jiashi earthquakes (Guo et al, 2002), the 2003 M6.8 earthquake (Huang et al, 2006), and the 1997 Jiashi earthquake swarm respectively (data from the GCMT catalog, https://www.globalcmt. (Xiao et al, 2002;Li et al, 2019;Zhang et al, 2019;Yao et al, 2019). The locations of the sections and the acronyms for the names of the faults are shown in Figure 1.…”

“…(Figure 1 Section A-A′, and B-B′) (Allen et al, 1999;Tian et al, 2016). The Kaping fold-and-thrust belt is segmented into eastern and western sections by the Piqiang fault that is a NNE-SSW-and NNW-SSE-striking oblique-slip deep-cutting fault (Yang et al, 2008a;Turner et al, 2011;Yao et al, 2019). In the western section, five major thrust-folds root into a décollement at ∼9 km depth (section A-A′ in Figure 2A) (Xiao et al, 2002;.…”

“…On January 19, 2020, the M6.4 Jiashi earthquake occurred along the Kaping fold-and-thrust belt (also called the "Kepingtage" or "Keping"), a well-known thrust fault zone in the southwestern Tien Shan Mountains, China (Yin et al, 1998;Allen et al, 1999;Turner et al, 2011). This south-verging (northdipping) fold-thrust belt propagates toward the northwestern margin of the Tarim Basin (or Tarim Craton), where the Paleozoic sedimentary cover is being actively deformed by some emergent thin-skinned thrusts (Jia et al, 1998;Lu et al, 1998;Allen et al, 1999;Zhang et al, 2019). For understanding the seismotectonics, more attention was paid to the actively deforming thrust faults and folds.…”

Forearc Basin Stratigraphy Resulting From Syntectonic Sedimentation During Accretionary Wedge Growth: Insights From Sandbox Analog Experiments

“…The formation of a forearc basin at an accretionary margin is controlled by deformation of the accretionary wedge, which depends on various factors including the material properties of the wedge and the décollement (friction, cohesion, and pore fluid pressure), plate convergence (obliquity and velocity), isostatic response (uplift and subsidence), and external surface processes (erosion and sedimentation) (e.g., Byrne et al, ; Fuller et al, ; Graveleau & Dominguez, ; Gutscher et al, ; Malavieille et al, ; Mannu et al, ; Noda, , ; Simpson, ; Wang & Davis, ). Among these factors, external surface processes can strongly influence deformation of the accretionary wedge (e.g., Cruz et al, , ; Simpson, ; Storti & McClay, ) by (1) concentrating deformation at the rear of the wedge (Hardy et al, ; Storti & McClay, ), (2) reducing the taper angle (Bigi et al, ; Simpson, ; Storti & McClay, ), (3) decreasing the number of thrusts and widening the thrust spacing, which is likely caused by a reduction in differential stress in the wedge due to an increase in normal stress (Bigi et al, ; Fillon et al, ; Liu et al, ; Simpson, ; Zhang et al, ), (4) increasing the duration of folding at the upper ramp tip (Storti et al, ), (5) prolonging the phase of underthrusting and limiting the forward propagation of thrust activity (Del Castello et al, ; Hardy et al, ), (6) forming a trishear zone and causing limb rotation (Wu & McClay, ), (7) creating and reactivating out‐of‐sequence thrusts (Mannu et al, ; Storti et al, ), (8) stabilizing the rear of the wedge and increasing the rate of migration of the deformation front (Fillon et al, ), and (9) causing a switch from frontal accretion to synchronous thrusting and underthrusting due to local heterogeneity of the basal shear stress (Bigi et al, ; Del Castello et al, ; Storti et al, ).…”