Shallow S-wave velocity structure in Chongqing area

Based on the teleseismic waveform data recorded at permanent stations in Chongqing and its adjacent area from January 2011 to October 2018, the shallow S-wave velocity structure beneath the stations of Chongqing and its surrounding area is calculated by the method to constrain shallow structure based on direct P-wave amplitude in receiver functions. The results indicated that, the velocity structure of shallow S-wave in Chongqing is obviously related to the basin mountain structure, the low velocity anomaly in the basin corresponds to the characteristics of sedimentary layer, and the Daba mountain and Dalou mountain regions show relatively high velocity anomalies. The S-wave velocity of Huayingshan fault is higher than that of sedimentary layers on both sides of the fault, implying that the sedimentary layers in Sichuan basin are thin in the middle and thick on both sides. Finally, we discussed the seismogenic environment of five earthquakes in Chongqing since 2010. The Dianjiang M_S4.4 earthquake and the Shizhu M_S4.5 earthquake located in the east Sichuan detachment structure area are related to the obvious low velocity anomaly. The Rongchang M_S4.7 and M_S4.8 earthquakes have no obvious characteristics of high or low velocities, which may be related to water injection. The Wulong M_S5.0 earthquake occurred on the high velocity body side that is conducive to strain accumulation of the high and low velocity junction.