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基于应用透射人工边界条件的显式有限元法,计算了断层破碎带宽度及其物理力学参数变化、入射地震动角度变化时二维断层场地模型地表地震动场的分布。结果表明:低速度断层破碎带的存在导致整个场地都有SV波转换为P波的分量,且在破碎带区域出现断层陷波;低速度断层破碎带的存在使输入场地恒定的能量向破碎带中集聚放大,且随着破碎带宽度增大或破碎带介质波速降低,集聚放大效应增大;场地放大效应是频率相关的,具有不同卓越频率的断层场地会有选择性地放大和场地卓越频率相近的地震动,破碎带宽度增大或介质波速降低时,断层场地的卓越频率降低,显著放大效应选择的地震动卓越频率也相应越低,即宽度较宽或介质波速较低的低速度断层破碎带场地的卓越频率较低,对输入场地的较低频率成分的地震动放大显著;竖向低速度断层破碎带能阻隔斜入射地震波,且随着入射角增加,这种隔震效应更显著。
Based on the explicit finite element method using transmission artificial boundary conditions, the width of fracture zone and its physical and mechanical parameters are calculated. The distribution of surface ground motion field in two-dimensional fault site model with incident ground motion angle changes is calculated. The results show that the existence of low-velocity fault fracture zone leads to the conversion of SV wave to P wave in the whole site, and the occurrence of fault notch in the fault zone. The existence of low velocity fault fracture zone causes the constant input energy to the crushing zone And the concentration amplification effect increases with the increase of the width of the crushing band or the decrease of the wave velocity of the medium in the crushing zone. The amplification effect of the site is frequency-dependent, and the fault sites with different superior frequencies are selectively magnified and the site superior frequency Similar earthquakes, the increase of the width of the crushing zone or the decrease of the medium wave velocity, the excellent frequency of the fault site decreases, and the remarkable frequency of the earthquakes with the magnifying effect is correspondingly lower, that is, the low-velocity faults with wide width or medium wave velocity The lower frequency of the crushing zone is more significant for the lower frequency components of the input field; the vertical low velocity fault crushing zone can block the oblique incident seismic wave, and the isolation effect becomes more significant as the incident angle increases .