Diachronous Quaternary Development of the Jiayuguan Fault and Implications for Strain Compartmentalization and Modern Earthquake Hazards in the NW Hexi Corridor, China

Abstract

The NNW‐trending Jiayuguan Fault (JYGF) is an actively developing thrust fault that delimits the SW margin of Jiayuguan, a major industrial city in the northwestern Hexi Corridor, China. In this study, we document the geometry, kinematics, and slip rates of the JYGF based on analysis of satellite imagery, low‐altitude photogrammetry, field observations, paleo‐seismic trenching, and Quaternary dating. The JYGF hanging‐wall contains a NE‐vergent asymmetric anticline of Cretaceous redbeds unconformably overlain by faulted, tilted and folded alluvial fan and fluvial terrace surfaces. Subsidiary fault scarps are associated with anticlinal flexure and contractional strain. The vertical uplift and crustal shortening rates are both ∼0.1 mm/a since ∼420 ka and geomorphic markers and dated landforms indicate southeastward fault propagation and hanging‐wall uplift from the Heishan toward the modern Beida River channel. The NW end of the fault appears to connect with the Altyn‐Tagh‐Heishan‐Jinta'Nanshan sinistral strike‐slip fault array suggesting that the JYGF is one of several parallel, splay faults that transfer strike‐slip motion to active folding and thrusting in the region. We relocate the 1992 Ms 5.4 earthquake epicenter using the NonLinLoc method and suggest that the JYGF may link southeastward with Quaternary‐active faults and folds in the Wenshushan. A seismic rupture along the total fault length of 25–40 km for the JYGF‐Wenshushan deforming belt corresponds to a potential earthquake magnitude in the 6.6–7.0 range. Compartmentalized faulting and folding in the NW–most Hexi Corridor defines a triangular block of active deformation where NE‐directed contractional deformation of the Qilian Shan foreland interacts with E‐W left‐lateral displacement along the Altyn‐Tagh‐Heishan‐Jinta'Nanshan sinistral strike‐slip system.

New Magnetotelluric Data Reveal Deep Fault Boundaries and Contrasting Late Cenozoic Fault Kinematics Between the Qilian Shan Thrust Wedge and Beishan‐Alxa Block, Western China

“…The R2/C2 boundary is spatially correlated with the surface exposure of the Jiayuguan dextral‐thrust fault. The shallow dip and resolved depth extent (∼4 km) of the JYGF is also constrained by deformed alluvial fans and terraces (Yang, Li, Cunningham, Zhan, et al., 2023). Under the Heishan, a wide low‐resistivity zone separates R3 from R4 and may extend to 20–30 km depth.…”

“…A steep HSF geometry is also compatible with geological observations of Quaternary strike‐slip landform offsets and a wrench style fold belt along the Heishan‐Jinta'Nanshan Fault which may represent the eastward continuation of the ATF system (Yang, Li, Cunningham, Yang, et al., 2023). A shallow fault separating R2 and C2 coincides with the SW‐dipping JYGF, and deformed Quaternary alluvial fan surfaces indicate that the JYGF is a transpressive splay fault of the Heishan‐Jinta'Nanshan sinistral strike‐slip fault system (Meyer et al., 1998; Yang, Li, Cunningham, Zhan, et al., 2023). No significant resistivity anomaly was detected in the mid‐lower crust of the Hexi Corridor basin between sites 302 and 334A (Figures 2 and 3) where we deployed very dense MT stations.…”