吸收介质中的Maslov体波理论地震图

MASLOV THEORETICAL SEISMOGRAM IN ATTENUATION MEDIUM

本文研究了横向非均匀吸收介质中的Maslov渐近理论地震图方法.对于如何提高计算精度及计算速度作了比较深入的探讨.本方法先计算远场格林函数,由褶积得到一般震源函数的弱吸收理论地震图.对于高Q引起的数值不稳定性,通过引入平滑函数得以解决.由此产生的新的被积函数具有非常好的收敛性,从而提高了计算精度及计算速度.以此理论编写的程序在模拟完全弹性介质以及一维吸收介质时与反射率法作了比较,并取得了令人满意的效果.对于二维横向非均匀吸收介质,计算方法与高斯光束方法作了对比,二者在主要特征上基本一致.数值对比中出现的一些差异也作了必要的讨论及说明.

This paper studies the Maslov asymptotic theoretical seismogram method in lateral heterogeneous attenuation medium. Deep discussion has been given for how to raise the computation precision and speed. The method calculates the far-field Green function first, and then the theoretical seismogram for general source function can be obtained by convolution. A smooth function has been introduced to solve the problem of instability caused by high value of Q. The newly constructed integrand has good property of convergence, thus raising the computation precision and speed. The results computed by the program based on this theory has been compared with the reflectivity method in modelling complete elastic medium and 1D attenuation medium, which gives satisfactory result. Comparation between the method and the Gaussian beam method has also been given for 2D lateral heterogeneous attenuation medium. Two methods are essentially consistent in major characters. Necessary discussions and explanation on some differences found in the comparation have also been given.