Strain Partitioning on the Western Haiyuan Fault System Revealed by the Adjacent 2016 <i>M</i><sub><i>w</i></sub>5.9 and 2022 <i>M</i><sub><i>w</i></sub>6.7 Menyuan Earthquakes
Heng Luo, Teng Wang
Abstract
Abstract The 1,000 km‐long Haiyuan fault is the largest strike‐slip fault system in the northeastern Tibetan Plateau, accommodating part of the plateau's eastward extrusion. However, few large earthquakes have been instrumentally recorded, hindering our understanding of strain partitioning across the fault system. Here, we use synthetic aperture radar images to investigate fault geometries and slip distributions of the adjacent 2016 M w 5.9 and 2022 M w 6.7 Menyuan earthquakes that occurred 35 km apart along the western Haiyuan fault system. The purely strike and purely thrust slips of the 2022 and 2016 events indicate that strain was released separately on shallow steep fault and low‐angle fault at depth. We propose that such strain partitioning is controlled by the ratio between interseismic shear and normal velocities and the branching fault structure beneath the Lenglongling segment. Seismic hazard due to both focal mechanisms has to be considered along the western Haiyuan fault in northeastern Tibet.