层状地壳模型地面地下记录地震波的理论地震图和频谱计算

THE COMPUTATION OF THEORETICAL SEISMOGRAMS AND SPECTRA OF SEISMIC WAVES RECORDED ON THE SURFACE AND UNDERGROUND OF STRATIFIED EARTH CRUST

本文首先发展了计算层状介质地面及地下记录地震波理论地震图的部分分离变量—有限差分计算方法,其最主要的环节是引进了吸收边界条件,使计算工作量大大减少,得以在实际工作中推广应用。其次,应用矩阵方法计算地面及地下记录的地震波的理论频谱。最后给出了用上述方法得到的华北地区两种不同的理论地壳模型情况下的理论地震图和频谱计算结果。应用这些理论结果,可根据实际地震观测资料对地壳介质模型进行分析、评判和优选。

The combinational method of partial separation of variables and finite differences has been applied to computing the theoretical seismograms of body waves recorded on the surface and underground of stratified media. For the simplification of numerical computation, the absorption boundary condition at an artificial boundary Z = L under the Moho discontinuity has been introduced. Second, the method of matrix has been applied to computing the theoretical spectra of seismic waves in stratified media.For the illustration of the methods, the theoretical seismograms and spectra for the two models of the stratified earth crust of North China have been obtained and analyzed. Among them the model A corresponds to the crust upper mantle structure of the Tangshan region and the model B is a simplified one of the crust. By using the theoretical results obtained, the models of the crust medium can be analyzed and assessed. And the optimum one may be chosen on the basis of the practical records of seismic waves observed on the surface and underground.