多水平成层的非均匀介质圆弧形峡谷地下多点地震动模拟

Simulation of spatially variable underground seismic motions in circular-arc canyons with horizontally-layered inhomogeneous medium

开发了考虑圆弧场地水平多分层效应的地下多点地震动模拟可视化程序,验证其可靠性。首先,描述了给出的圆弧场地多分层效应的SH波动散射频域解,其本质是突破了传统均匀介质和分层不穿越峡谷前提的局限性;其次,利用从水平地表到峡谷表面再到地下土层的传递函数,通过两次传递得到了圆弧峡谷地下的目标功率谱和反应谱;进而,具体描述所导出的圆弧场地平-凹相关性的相干函数及其推导过程;最后,基于上述理论,开发了多层状的非均匀圆弧场地的多点地震动模拟程序,给出了模拟结果与目标功率谱、反应谱和相干函数的拟合对比,验证了该理论和程序的合理性和可靠性,便于所发展理论和方法的实用化和推广。

In this paper,a visual program for simulating spatially variable underground seismic motions in circular-arc canyons taking the horizontally-layered effect into account is developed,and the reliability of the program is verified.Firstly,the frequency-domain solution for the scattering of SH waves by a circular arc considering horizontally-layered effect is described.The essence of it is to break through traditional theoretical limitations of homogeneous medium and canyons do not pass through multi-layer soil.Secondly,a two-step transfer function method combining the transferring from flat-ground terrain to the canyon surface （step one） with the transferring from the canyon surface to underground location （step two） is adopted to derive the underground target PSD and response spectrum of circular-arc canyons.And then,the coherence function taking account of the flat-concave correlation of circular-arc field and its derivation are described in detail.Finally,aiming to provide convenience for further development and application of the simulation theory above,a program for simulating underground seismic motions in circular-arc canyons taking account of horizontally-layered effect is developed and the comparison between simulated and target results including PSD,response spectrum and coherence coefficient is given,which further verifies the rationality and reliability of the method.