P,SV波斜入射下凹陷地形地震动分布特征

Characteristic of ground motions of a canyon topography under inclined P and SV waves

采用数值模拟方法,探讨了凹陷地形在P波和SV波斜入射下,入射角度θ和凹陷深宽比H/L等参数的变化对地表地震动峰值放大系数β的影响。得到如下结论:(1)峰值放大系数的影响程度和范围受不同地震波的影响较大;(2)凹陷两侧的放大系数比底部大,凹陷两侧顶点的放大系数比两侧地表的大;(3)凹陷深宽比一定,SV波从左边斜入射,放大系数随入射角的增大而增大,x分量的放大系数大于z分量,左顶点放大系数大于右顶点,对于P波,x分量的放大系数小于2,放大系数随着入射角的增大而增大,凹陷两侧顶点的z分量放大系数大于2,放大系数随着入射角的增大而减小;(4)入射角θ不变,无论是SV波还是P波,左右两侧的放大系数随凹陷深宽比H/L的增大而增大。当SV波从左边斜入射时,x分量左顶点的放大系数大于右顶点,z分量放大系数小于x分量;当P波从左边斜入射时,左顶点x分量放大系数大于右顶点,所有放大系数均小于2,z分量放大系数大于x分量。这些结论可为实际工程提供参考。

Seismic ground moti o n of a c a n y o n topography u n d e r left inclined incident P and SV waves was analyzed using a numerical simulation method. The effects of the incident angle a n d the aspect ratio （ ratio of the c a n y o n d epth and width） on the ground moti o n amplification factor of the surface w e r e discussed. It is s h o w e d that： （1） the influence degree and range of the p are strongly related to the incident w a v e s. （2） ^0 of the c a n y o n ^ s side is generally larger than the bottom, and p of the side comer is larger than the top surface. （3） F o r fixed aspect ratio a n d S V w a v e i n c i d e n c e, the amplification factor increases with incident a n g l e, and /3 of the x c o m p o n e n t is greater than the z c o m p o n e n t. B e s i d e s, /3 ofleft side comer is larger than the right. Fo r P w a v e i n c i d e n c e, /3 of the x c o m p o n e n t is less than 2, a n d /3 is also increaseing with the incident a n gle. The z c o m p o n e n t amplification factors at the t wo side c o m e r s of the c a n y o n e x c e e d 2, and p decreases with 〇. （4） Fo r fixed 0, n o matter of SV a n d P w a v e i n c i d e n c e, p of the c a n y o n ^ s t wo sides increases with the aspect ratio. For SV wave i n c i d e n c e, /3 of the x c o m p o n e n t at the left side c o m e r is greater than the right o n e s,and /3 of the z component is less than the x. Fo r P w a v e i n c i d e n c e, /3 of the x c o m p o n e n t at the left side c o m e r is also greater than the right ones, with j 3 at a n y positions less than 2, a n d /3 of the z c o m p o n e n t is larger than the x c o m p o n e n t.