SV波入射情况下V型河谷地形对地震动的影响分析  

Influence of V-shaped canyon site on ground motions for incident SV waves

作　　者：刘必灯[1] 周正华[1] 刘培玄[1] 李小军[2] 王伟[1] 

机构地区：[1]中国地震局工程力学研究所,黑龙江哈尔滨150080 [2]中国地震局地球物理研究所,北京100081

出　　处：《地震工程与工程振动》2011年第2期17-24,共8页Earthquake Engineering and Engineering Dynamics

基　　金：中国工程院重大咨询专项(2010-ZD-4);国家自然科学基金重大研究计划资助项目(90715042;90715038)

摘　　要：基于局部人工边界的显式有限元方法,给出了二维V型河谷地形在SV波垂直入射下地面运动数值解,并分析其地震动分布规律以及两侧不同的边坡角度对于地震动分布规律的影响。数值结果表明:谷底的角点、两岸靠近河谷的点、两侧谷坡靠近谷底的点以及靠近两岸的点,对地表位移有放大作用,而对其邻近区域地表位移有抑制作用。这是由于角点处存在面的相交和转化,使角点处和角点附近波的散射更为复杂,故波形转换更加强烈,并且以其为中心有一定的影响区域,越靠近这些角点波形转换越为强烈。峰值结果、传递函数结果和观测点质点运动轨迹结果都显示了这一规律。整体而言,右岸和右坡坡顶附近波形转换要比左岸明显得多,且对应两侧河岸相同的X向位移峰值,左侧河岸的影响范围要比右侧的影响范围大,这可能是因为右坡坡度更大导致波形转换要更强所致。两侧河岸质点运动轨迹最终都呈现逆进运动轨迹,有些观测点的逆进椭圆轨迹较明显,这可能是由于在河岸处SV波转换成面波所致。A numerical solution to the 2D model of V-shaped canyon under the normal incident SV waves is derived by using the explicit finite element combining local artificial method,and the distribution rule of site ground motions and the effect of different slope angles on influence range of bank PGD are discussed.Based on the numerical results,it is found that the surface ground motions at the intersecting positions of valley bottom and the slope,the slope and the bank are great while the adjacent regions of these points is constrained.This may be due to the scatter of the SV wave and the wave-type conversion is rather complicated at the intersecting positions.And the closer to the intersecting position,the stronger the scatter waves appear.The rules above are proved by the results of PGD,amplitude of transfer function and particle motions.The wave-type conversion of the right bank and the right slope top is greater than that of the left side,and the influence range of the left bank is larger than that of the right bank,because the right slope angle is larger than that of the right side.The particle motion coda on both sides of the bank is viewed as the backward motion,and the backward elliptical motion of some observation points are very obvious.These calculations predict that at the bank on both sides the normally incident SV wave may be converted into Rayleigh wave.

关 键 词：V型河谷 SV波垂直入射 传递函数 波形转换 质点运动轨迹 逆进椭圆 

分 类 号：P315.9[天文地球—地震学]