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Relocation of the 2019 Changning Ms6.0 Earthquake Sequence and Apparent Stress Analysis

Session: New Insights Into the Preparatory Phase of Earthquakes From Tectonic, Field and Lab Experiments III

Type: Oral

Date: 4/19/2021

Presentation Time: 05:45 PM Pacific

Description: 

Recently, the seismicity of Sichuan Changning area presents the tendency of higher frequency and larger intensity. Considerable earthquake monitoring and scientific studies show that the change of seismicity in industrial activity is related to the activities of waste water injection and hydraulic fracturing. On June 17, 2019, an earthquake of M_S6.0 struck Changning County, and four aftershocks with magnitude larger than M_S5.0 occurred during the following days till to July 4, 2019. According to the history record, there is no any other earthquakes with magnitude larger than the Changning M_S6.0 earthquake in this area. In this study, based on the seismic data provided by China Earthquake Networks Center, we relocated the M_S6.0 Changning earthquake sequence from June 17 to December 31, 2019 by using double-difference location method. Meanwhile, the apparent stress of 103 M_S≥3.0 earthquakes before December 31 were also calculated. Finally, the seismogenic structure of the sequence is preliminarily analyzed.

The distribution of relocated 5400 M_L≥0.0 events shows that the aftershock area is 25 km long and 5~8 km wide in a NW-SE trending. The focal depths range from 0 to 10 km and the total sequence is deep in the west and shallow in the east. The M_S6.0 earthquake is relocated at the southeastern end of the aftershock zone, showing its unilateral rupture behavior. According to the aftershocks upon the mainshock, there may exist an unnamed small scale fault. By analyzing the calculated apparent stress of earthquakes occurred from 2017 to 2019, we obtained two conclusions: (1) The stresses of M_S3.0~3.4 earthquakes were at a relative high level before the M_S6.0 earthquake, while the stresses of M_S≥3.5 earthquakes did not emerge high values. (2) Six of the seven M_S≥4.5 earthquakes after the main shock were preceded by high apparent stresses of M_S3.0~3.4 earthquakes. Thus, for Changning area, the high apparent stresses of M_S3.0~3.4 earthquakes may be useful for prediction of M_S≥4.5 earthquakes.

Presenting Author: Yue Wang

Student Presenter: No

Authors