43 / 2025-07-16 08:40:09

Induced Moderate Earthquake by Hydraulic Fracturing in Shale Gas Development: A Case Study of Weiyuan, Sichuan, China

Sichuan Basin,Induced earthquake,pre-existing fault,Coulomb failure stress,InSAR data inversion

    Weiyuan Anticline is located in the transitional zone between the Sichuan Basin and the western mountainous region, having undergone multi-phase tectonic superimposition throughout its geological history. The region is subjected to complex stress conditions, influenced by both NW-oriented compression from the Longmen Shan thrust belt and near-EW-directed thrusting from the Daliang Shan toward the basin interior. Historically, seismic activity in the Weiyuan area has been relatively weak. According to historical records, only five moderate earthquakes have occurred since 1896.

    However, since 2014, both the frequency and magnitude of seismic events have increased annually, peaking in 2019. Notably, three moderate earthquakes（M_S 4.7, M_S 4.3, and M_S 4.9）struck western Weiyuan between February 24 and 25, 2019, followed by two additional events （M_S 5.4 and M_S 5.2） in eastern Weiyuan on September 8 and December 18 of the same year. Existing studies have different understandings on key aspects of these five moderate earthquakes, including: The centroid depths of the events; the causative faults responsible for the seismicity, and the underlying seismogenic mechanisms.

    To address these questions, this study integrates two-dimensional （2D） seismic reflection profiles and high-resolution three-dimensional （3D） seismic reflection data, calibrated with drilling data to delineate and interpreter stratigraphy. Additionally, we conduct detailed interpretations of the geometric configurations of blind faults within the shale gas development zone reconstructing their 3D structural models. By further synthesizing InSAR data and seismological datasets we jointly constrain the seismogenic faults and analyze earthquake interactions and triggering mechanisms. These findings will serve as a guideline for pre-existing fault avoidance in hydraulic fracturing well design, evaluation of potential slip hazards from concealed faults, and the promotion of safe shale gas extraction in the Weiyuan development zone.