Two-dimensional simulation of high-frequency scattering of seismic waves by local sites based on fast multi-pole boundary element method

A new high-precise fast indirect boundary element method is developed to solve the two-dimensional scattering problems of high-frequency seismic waves (2D in-plane) based on the fast multi-pole expansion technique. It is verified that this method has high accuracy, efficiency and excellent numerical stability, and can greatly reduce the computational storage. Taking the seismic response of a canyon and a hill in a half space under high-frequency incident plane SV waves as an example, the basic characteristics of high-frequency scattering around the canyon and hill are discussed, and the scattering results of 0~25 Hz broadband waves by large-scale local sites of thousands-meters are illustrated. The numerical results show that under the high-frequency incident SV waves, the amplification effect of the canyon on the horizontal and vertical displacement under high-frequency incident SV waves can be seen clearly at the corner of the canyon, but seems not so pronounced at the bottom of the canyon. The spectral peak of displacement amplitudes reaches up to 5.0 near the top of the hill, while the displacement response at the foot of the hill is constrained. As for the obliquely incident SV waves, the displacement at the canyon surface is more pronounced, but the amplification effect is more significant at the back of hill surface. The numerical results may provide a theoretical basis for the seismic design of large-scale projects constructed in complex local sites.