弹性半空间位错内源的数值解
NUMERICAL SOLUTION OF WAVE FIELD NEAR A DIS- LOCATION SOURCE IN AN ELASTIC HALF-SPACE
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摘要: 本文首先将一般剪切位错点源表示成四种基本点位错的组合,断层面倾角和滑动系数仅与组合系数有关.利用将三维动力学问题化为两维的处理方法,将每一基本点源问题化成求解位移函数的轴对称问题,最后将人工透射边界的处理方法同有限差分结合起来,提出一种简便、节省的计算理论地震图的方法.利用这种方法获得了四种基本点位错源的典型近场理论地震图,并初步讨论了近场地面运动的若干特征,表明浅源地震近场地面位移中震相不能分离,且点位错源在近场产生大小相当的水平与垂直位移.本文的方法可用于研究复杂的近场地震波传播问题.Abstract: A less-costly numerical method is developed to obtain the theoretical seismograms at locations near a seismic source in an elastic half-space. An arbitrary shear dislocation point source is first considered as a linear combination of four basic ones, their combination coefficients are determined by the fault dip angle and slip direction. Each basic point source problem is then reduced to an axis-symmetric problem which is solved by the numerical method combining finite difference method and a new scheme dealing with the artificial boundary. By comparing the method of this paper with the present available analytical method, it can be concluded that the method of this paper consumes much less computer time for complicated near field problems.A set of near field theoretical seismograms for the basic dislocation point sources is presented and some features of near field ground motion, such as the horizontal displacements may be of about the same magsitude as the vertical ones and etc., are discussed.The numerical method of this paper can easily generalized to resolve problems of a finite shear dislocation source in a layered medium. Puthermore, it can be applied to study more complex near field wave propagation problems.