Seismogenic Structure and Mechanism of the Ms6.0/Mw5.8 Sichuan Changning Earthquake

Session: Mechanisms of Induced Seismicity: Pressure Diffusion, Elastic Stressing and Aseismic Slip [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

On June 17, 2019, a M_S 6.0 earthquake occurred in Changning, Sichuan Province. It is the largest earthquake of the instrumental record in the Sichuan Basin and caused severe disaster. Since the location of the Changning earthquake is near the salt mine and shale gas wells, the mechanism and its seismogenic structure are being hotly debated. In this study, we obtained accurate locations of 5,013 earthquakes and simulated the seismogenic fault of this earthquake, which revealed a complex geometry of the fault with the opposite inclination along the fault and branch faults existing at both ends. High dip-angle is another characteristic of the seismogenic fault. The seismic region can be divided into two parts, in which the Coulomb stress caused by the mainshock triggered the aftershocks in the northwest segment of the source area. Since the earthquake activity of the Changning anticline has been frequent in the past 40 years, this earthquake is a devastating event that occurred in the area with high background seismicity. The length of active faults in the source area is so small that they are difficult to generate a M_S 6.0 earthquake. Low resistivity and relatively high Poisson’s ratio around the mainshock indicate possible fluid activity in the source region. We infer that pre-existing high-angle fault along the axial direction of the fold zone was reactivated by the fluid intrusion and caused the Changning earthquake.

Presenting Author: Lihua Fang

Authors