中文摘要：

震害现象显示在一些覆盖层很薄的基岩河谷山区地震动分布差异明显。为了厘清各形状要素的均质地形模型对地震动特性的影响,侧重分析了河谷坡角、坡高及不对称坡体等要素对均质体河谷模型的地震动（PGA）的影响。研究结果表明：河谷地形谷底内部的地面运动幅值在坡角40°～50°范围内达到最大值;在高坡角的河谷内波衰减比较慢,波形相对较复杂;在深宽比较小时,高频和低频脉冲的地面加速度峰值都呈现同样的变化趋势,且谷底地面各个位置PGA变化不明显,随着深宽比的增加,高频脉冲的地震反应变化复杂,出现谷底中心加速度幅值大于山脚;河谷的不对称形状对谷底PGA有影响,谷底PGA最大的位置靠近坡高小的一侧,且坡角大的一侧山脚附近谷底PGA要小一些,即坡度和高差越大,会很大程度地增加河谷两侧坡体的临空面,并增大地震加速度的放大系数,凸起地形对地震响应有放大作用,对它附近区域却有抑制作用,而且坡高、坡角越大,抑制作用越明显。

英文摘要：

The earthquake damage phenomenon indicates that the distribution of earthquake ground motion differs significantly in various parts of bedrock valley areas.The amplitude of ground motion has an important direct impact on the extent of the seismic hazard;larger amplitudes result in more severe disasters.Many towns located in the valley areas are widely distributed over Shanxi,Gansu,and Sichuan provinces and sustain severe damages from earthquakes.Research on this type of area has recently increased with particular emphasis on valley terrain.Many scholars have reported that input data is a significant problem for calculating the parameters of ground motion during strong shocks in such cities because microzoning is often closely related to the characteristics of soil strata and the geomorphological conditions.Nevertheless,the conditions of terrain and geology are interdependent with each other and have an impact on ground motion;it is widely accepted that terrain has an important effect on ground motion.Common valley terrain can be divided into three categories including V valley,inverted trapezoidal valley,and trapezoidal valley.V valley and inverted trapezoidal valley are widespread and are the topics of numerous studies.The bottom of V valley is narrow,and many geological disasters such as rockfalls occur in trapezoidal valleys.The inverted trapezoidal valley is more suitable for residency;therefore,research on this type of valley terrain is important.Because the drainage systems and valley landforms are generally not symmetric,homogeneous terrain models with various slope angles,depth-to-width ratios,and asymmetry of valley are used to analyze the variation of peak ground acceleration（PGA） in valley areas.By comparing the PGA,seismic spectra,and acceleration time history,the relationship between ground motion and topography is analyzed in this study.The results show that 1） the ground motion amplitude at the valley bottom appears to reach maximum value when the slope angles are approximately 40°~50° and