二维弹性波的有限元模拟及其初步实践

本文讨论了二维介质中弹性波有限元模拟的一种方法;导出了二维无界空间中集中力点源的理论初动表达式和位移波形表达式,并和相似情况下的有限元结果进行了比较;对用有限元方法算得的几个中小模型的节点位移进行了分析。从所能鉴别的震相的到时、初动符号分布、波形、瑞利波质点运动轨迹等证据看,在得到比较真实的全波理论地震图方面,有限元方法具有很大的潜力。

FINITE ELEMENT MODELLING OF ELASTIC WAVE PROPAGATING IN 2-D MEDIA AND ITS PRELIMINARY APPLICATIONS

In this paper an algorithm of finite element modelling is discussed for elastic wave propagating in two dimensional media. Two analytical formulas of the initial motion and wave form of P wave are derived in time domain for a point force source directing vertically down as a function of time with a bell shape. Then the theoretical distribution of initial motion are compared with the results obtained by the finite element algorithm with 16 × 22 node points under similar conditions. The agreement is well. Analysis of various evidences for several cases including the arrival times, the distribution of initial motions, the wave form, and the motion of particles in a Rayleigh wave at the surface indicates that the finite element algorithm used here is more practical and has great potential in calculating real full wave synthetic seis-mogram.