Three moderate-magnitude earthquakes in the western Kunlun Range piedmont in 2021 and 2022: Generated by the frontal blind ramp of the foreland thrust system

Summary

After the 2015 Ms 6.5 Pishan earthquake, three moderate-magnitude earthquakes, the Ms 5.4 Pishan earthquake on September 4, 2021, the Ms 5.4 Yecheng earthquake on September 5, 2021 and the Ms 5.4 Pishan earthquake on October 23, 2022, occurred in the seismically active western Kunlun Range foreland thrust system. The seismogenic structures responsible for the three most recent earthquakes and their relationships with the 2015 Ms 6.5 Pishan event are still not understood. Integrated analysis of relocation results of the three main events and their aftershock sequences, focal mechanism solutions, and regional geology has identified the seismogenic fault and structural geometry near the earthquake source. Our results recognize a gentlely S-dipping Kuoshi fault ramp, which is the frontal structure at the west part of the WKFTS and is responsible for the three most recent moderate-magnitude earthquakes. The 2015 Ms 6.5 Pishan earthquake and the recent moderate-magnitude events were all generated by the frontal fault ramp, indicating a deformation pattern characterized by simple outward thrusting. In the western Kunlun Range foreland, the most active deformation and topographic growth have migrated northward relative to those of the higher terrace folds as the rear ramp slip ceases. Our results provide new insights into deformation pattern and seismic hazard in the region.