The 3rd Badong International Geohazards Symposium (BIGS2021)

The seismicity in the Zigui area increases significantly and several earthquakes with M≥4.0 occurred since the impoundment of the Three Gorges Dam in 2003. At present, the seismogenic environment of the earthquakes remains controversial. In order to study the influence of the Yangtze River on deep faults and the seismogenic environment, we deployed 24 temporary seismic stations in the Zigui area in 2020 and recorded successive data for one month. Using the waveforms of the vertical component, we extracted the empirical Green's functions between any two stations by ambient seismic noise method and calculated the Rayleigh wave group velocity dispersion curve at periods of 0.6-4.8 s in the study region. The results show that there are significant differences in velocity structure between the Zigui basin and the eastern fault area. In each period (Figure 1), the group velocity in the Zigui Basin is generally lower than that of the neighbouring eastern fault area. Earthquakes of M≥4.0 occurred in the junction area of the high-/low-velocity. The velocity in the fault zone decreases quickly around the Yangtze River, indicating that the water of the Yangtze River has an impact on the underground structure.