摘要
在地震工程中,经常观测到地震波受地表起伏的影响而产生地形效应.本文基于数值模拟,研究了地震远场区域起伏地形对地表瑞利面波传播影响和对应的地形效应特征.结果表明:起伏地形的转折点或面的散射或反射,产生反方向传播的反射RR波和向空间扩散传播的转换RS体波,导致通过地形的瑞利面波能量极大的减弱,地形总体表现出强的隔震效应.地形起伏与地震动的波长比越大,隔震效应越强.凹陷地形表现出远比隆起地形更大的隔震效应.起伏地形转折引起的地表张角变化,导致地震动能量分布密度改变,是地形出现局部放大或减弱特征的主要因素.地表张角小于180°,地震动放大,张角越小放大作用越明显.地表张角大于180°,地震动减弱,张角越大减弱作用越强.当地形对地震动产生放大作用时,地震动水平分量比垂直分量放大效果更明显,而当地形产生减弱作用时,相对于水平分量,垂直分量更容易被减弱.
In earthquake engineering,topographical effects on the ground motion caused by rugged terrain have been frequently observed.In the present paper,based on the numerical simulation,the effects of Rayleigh surface wave propagating along the rugged terrain are studied which are dominant in the far-field area.The results first show that due to the reflected RR and converted RS waves caused by the reflection,or diffraction of topographic turning point or surface,can greatly reduce the energy of propagating Rayleigh surface waves,all the topography show strong vibration isolation effects.With the increasing of the ratio of wavelength to topography scale,the vibration isolation effect increasing.The depression terrains show much strong vibration isolation effects than that bump terrains do.On the other hand,the energy density change caused by the varying surface angles of rolling topography turning point is the main factor for local vibration amplify,or reduce of the topography.When the angle is less than 180°the vibration amplitude increases with the angle deceasing.When the angle is large than 180°,the vibration amplitude decreases with the angle increasing.Moreover,for the topography amplify effects of the horizontal component is much higher than that of the vertical component,while the topography reduce effects of the vertical component is much stronger than that of the horizontal component.
作者
肖薄
刘争平
黄云
曾胜强
李京京
奉建军
XIAO Bo;LIU Zheng-ping;HUANG Yun;ZHENG Sheng-qiang;LI Jing-jing;FENG Jian-jun(Southwest Jiaotong University,Chengdu 610031,China;China Railway Academy Company Limited,Chengdu 610032,China)
出处
《地球物理学进展》
CSCD
北大核心
2019年第3期1221-1228,共8页
Progress in Geophysics
基金
国家自然科学基金“山区深部岩体结构的瑞利面波椭圆极化特征研究”(41274107)资助
关键词
瑞利面波
地形效应
地形陡度
地表张角
有限元法
Rayleigh surface wave
Topographical effect
Terrain gradient
Topographical angle
Finite element
