Spectral element method simulation of three-dimensional sedimentary basin under reverse-fault earthquakes

Near-fault ground motion can cause serious earthquake disaster in the near-field area, especially when there is sedimentary topography in the area. At present, there are no reports on the ground motion response of sedimentary basins under the action of thrust faults which release more energy and have more destructive force. In this paper, spectral element method is used to establish the overall physical model of the dynamic source containing the reverse fault and the three-dimensional sedimentary basin. The dynamic response of the three-dimensional sedimentary basin under the dynamic reverse fault seismic action is studied. Taking an ellipsoid sedimentary basin as an example, this paper analyzes the characteristics of the ground motion response of its reverse faults, and discusses the time-history and peak variation of the ground motion at the observation points in the sedimentary basin under different wave velocity ratios and thickness of the sedimentary medium. The results show that: ① The wave velocity ratio of medium inside and outside the sedimentary basin has a significant influence on ground motion in the sedimentary basin. When the wave velocity ratio of medium inside the sedimentary basin decreases, the peak response on the surface inside the basin increases, and the duration of ground motion significantly extends. In particular, the peak acceleration in the center of the basin magnifies by 2.08 times, and the duration extends by 1.97 times; ② The thickness of a sedimentary basin also has an impact on its ground motion response. When the sedimentary thickness increases, the ground motion response at the center of the basin decreases by 0.64 times, while the ground motion response at the edge of the basin increases significantly, by about 1.35 times.