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结合快速多极子展开技术与间接边界元法,发展一种新的高频地震波散射(二维平面内)快速模拟方法。精度和效率检验表明该方法具有很高的计算精度、求解效率及良好的数值稳定性,同时可大幅度降低计算存储量。进而以半空间峡谷与凸起地形对平面SV波的高频散射为例,讨论了峡谷及凸起周围地震波宽频散射基本特征,给出了千米尺度局部场地、0~25 Hz频带宽度的散射模拟结果。分析表明:高频SV波垂直入射下,峡谷角部水平和竖向位移均表现出明显的放大效应,而峡谷底部的散射效应较弱;半圆凸起顶部附近水平位移谱峰值高达5.0,山脚处位移反应则受到明显的抑制作用;斜入射情况,峡谷地形迎波面一侧位移幅值较大,而凸起地形则是背波面一侧放大显著。数值结果可为复杂局部场地中大型工程抗震设计提供部分理论依据。
Combining the fast multipole expansion technique with the indirect boundary element method, a new method of rapid simulation of high frequency seismic wave scattering (2D in-plane) is developed. Accuracy and efficiency tests show that this method has high computational accuracy, solving efficiency and good numerical stability, while significantly reducing the calculation of storage capacity. Taking the high-frequency scattering of planar SV waves in half-space canyons and raised terrain as an example, the basic characteristics of wide-band scattering of seismic waves around canyons and bosses are discussed. The scattering of 0-25 Hz band width at local scale on km scale is given Simulation results. The results show that the horizontal and vertical displacements of the canyon at both corners of the canyon show a significant magnifying effect under the normal incidence of high frequency SV waves and the scattering effect at the bottom of the canyon is weak. The peak value of the horizontal displacement near the top of the semicircular bump reaches up to 5.0, Displacement reaction was significantly inhibited; oblique incidence, gorge topography wave amplitude displacement side of the larger, while the convex topography is the back side of the wave amplification significantly. The numerical results can provide some theoretical basis for the aseismic design of large-scale projects in complex local sites.