Seismicity and seismogenic mechanism of the MS 6.0 Luxian earthquake on September 16, 2021

Abstract

Based on the seismic data recorded by the China Earthquake Networks Center (CENC) in the Luxian area from January 2009 to October 2021, the 3D V_P, V_S, V_P/V_S structures and seismic locations of the area are obtained by joint inversion using the V_P/V_S model consistency-constrained double-difference tomography method (tomoDDMC). The earthquakes in the study area are mainly concentrated at a depth of 2–6 ​km, and the focal depth is generally shallow. The M_S 6.0 Luxian earthquake occurred at the transition zone of high- and low-velocity anomalies and the aftershock sequence was distributed along the edge of the low-V_P zone. A small number of foreshocks occurred on the west side of the M_S 6.0 Luxian earthquake, while most of the aftershocks were distributed on the east side of the M_S 6.0 Luxian earthquake. The aftershock sequence consisted of three seismic bands with different trends, and the overall distribution was in a NWW direction, which was inconsistent with the spatial distribution of the main active faults nearby. In addition, the spatiotemporal distribution of earthquakes and the variation of b-values are closely related to the industrial water injection activities in the study area, reflecting the activation of pre-existing hidden faults under certain tectonic and stress environments leading to seismic activities in the area.