弹性介质面波地脉动单点谱比法研究

Research on spectral ratio of horizontal to vertical component for elastic model and surface microtremors

摘要: 应用概率统计方法,采用弹性成层介质模型,导出地下体波斜入射成层介质,在自由表面形成面波地脉动的水平分量与竖向分量谱比表达式。然后,通过大量模型计算,论证体波斜入射单层覆盖半空间形成面波地脉动水平分量与竖向分量谱比特性与场地传递函数间的关系。结果表明:利用地脉动单点谱比法分析面波为主要成分地脉动时,不能求出场地放大因子;当覆盖层与下伏基岩的S波阻抗比小于2时,也不能得到场地卓越频率;当阻抗比大于2时,可近似得到场地卓越频率。文中给出了一个场地基阶卓越频率fs与基阶瑞利波峰值卓越频率fR的计算公式:fS=0.8fR+0.06。

Abstract: The rationality for spectral ratio method of horizontal to vert ical component （ H/V method） for microtremors is discussed with a model of an elastic laye r over a half-space.The H/V expressions of surface microtremors for l ayered media are derived.The feasibility of estimating the horizontal transfer f unction from H/V of surface microtremors is discussed.It is shown that the spectral ratio method of horizontal to vertical component can be used to estimat e the site predominant frequency for surface microtremors when the impedance rat io is larger than 3.The relationship between s ite frequency and surface microtremors is f_S=0.8f_R+0.06 .Howe ver the amplification factor of site is difficult to be decided by H/V meth od.