摘要
The Changning region,located in the southern Sichuan Basin,has historically been regarded as tectonically stable.However,in recent years,seismicity has increased significantly alongside the expansion of large-scale industrial activities.The successive occurrences of the Xingwen MS5.7 and Changning MS6.0 earthquakes within a short interval have attracted considerable attention from both the seismological community and the public.To better understand the relationship between industrial activities and subsurface velocity structures,as well as their influence on seismicity,this study first selects a large number of high-quality P-and S-wave first arrival times from a dense array of temporary broadband seismic stations,and then conducts local earthquake traveltime tomography to invert for high-resolution P-and S-wave velocity models in the shallow crust beneath the Changning hydraulic fracturing zone.The results reveal that velocity heterogeneities are generally correlated well with stratigraphic age,while localized velocity anomalies near industrial extraction layers are associated with injection pressure variations.Moreover,a low P-wave velocity anomaly forms a continuous belt linking the Xingwen and Changning seismic zones,indicative of a deep subsurface fluid migration channel.Although alternative seismogenic mechanisms cannot be ruled out,this finding preferentially supports a hypothesis in which fluid migration along a long-distance channel activated by the Xingwen earthquake contributes to the initiation of the Changning earthquake.
基金
supported by the National Key Research and Development Program of China(Grant No.2020YFA0710600)
the National Natural Science Foundation of China(Grant No.U23A2029)。
