A Study on Induced Seismic Activities in Southeast of Sichuan Basin, China, Using a Local Temporary Network

Abstract:

Induced seismic activity is becoming more and more severe in recent years near southeast of Sichuan basin, China, as the rapid development of Shale Gas exploitation around the local area. An earthquake with the magnitude of M_S 5.7 occurred near Xingwen County on 16 December 2018 within the Sichuan basin which is the largest hydraulic fracturing (HF) earthquake in the world to date and caused ground motions intense enough to be felt, triggered landslides, caused ￥50 million in direct economic losses, injuries, and resulted in the first fatalities (Lei et al., 2019; Long et al., 2020). Besides, 7 earthquakes with the magnitude greater than M_S 5.0 have taken place within Southeast of Sichuan basin since 2018 supposed either caused by HF operation or induced by wastewater disposal, where seismic activity has been low historically. The tomoDD double difference tomography method (Zhang and Thurber, 2003) has been applied to get the high-resolution three-dimensional structures, along with accurate locations of small earthquakes in the study area, taking advantage of a 21 mobile stations’ temporary network. Combined with the inverted structure and events’ location data, along with the local geological structural information and positions of HF well pads, we had a better understanding about the seismogenic structures of some moderate to strong earthquakes occurred in Sichuan basin and spatial relations between well pads and induced seismic activities. Further study is necessary especially with the supplementary operational times data of HF so as to infer the temporal relationship with the HF operation and induced seismic activities in the study area. And these studies can help to establish a suitable regulation controlling system for a safely development of shale gas resources in Southeast of Sichuan basin as there is no one yet to date.