SIMULATING SEISMIC-WAVE PROPAGATION IN 3D ELASTIC MEDIA USING STAGGERED-GRID FINITE-DIFFERENCES

This article provides an overview of the application of the staggered- grid finite-difference technique to model wave propagation problems in 3D elastic media. In addition to presenting generalized, discrete rep resentations of the differential equations of motion using the stagger ed-grid approach, we also provide detailed formulations that describe the incorporation of moment-tenser sources, the implementation of a st able and accurate representation of a planar free-surface boundary for 3D models, and the derivation and implementation of an approximate te chnique to model spatially variable anelastic attenuation within time- domain finite-difference computations. The comparison of results obtai ned using the staggered-grid technique with those obtained using a fre quency-wavenumber algorithm shows excellent agreement between the two methods for a variety of models. In addition, this article also introd uces a memory optimization procedure that allows large-scale 3D finite -difference problems to be computed on a conventional, single-processo r desktop workstation. With this technique, model storage is accommoda ted using both external (hard-disk) and internal (core) memory. To red uce system overhead, a cascaded time update procedure is utilized to m aximize the number of computations performed between I/O operations. T his formulation greatly expands the applicability of the 3D finite-dif ference technique by providing an efficient and practical algorithm fo r implementation on commonly available workstation platforms.