ELASTI

Abstract

The mathematical underpinning of algorithm ELASTI is the so-called velocity-stress system of coupled partial differential equations governing linear (i.e., infinitesimal deformation) seismic wave propagation within a three-dimensional isotropic elastic body The medium is characterized by the three parameters: compressional (P) wave speed, shear (S) wave speed, and mass density, all of which may vary in the three spatial dimensions. The nine dependent variables (three particle velocity vector components and six stress tensor components) are stored within the algorithm on staggered spatial and temporal grids. The 3D spatial grid is rectangular, and grid intervals are uniform in each coordinate direction. Numerical solution methodology consists of explicit, time-domain, finite-differencing. Discrete finite-difference (FD) operators approximating partial derivatives possess 2nd-order accuracy in time and 4th-order accuracy in space. FD formulae for updating the wavefield variables are appropriately non-dimensionalized and normalized so that single-precision arithmetic calculations yield 1105824/01 adequate accuracy. This software will be used to generate seismic responses for typical geological/geophysical models of interest in the petroleum, mining, geotechnical, geothermal, hydrological, environmental assessment, and underground storage industries. Additionally, US government agencies (including the military) involved in monitoring of explosions or remote surveillance of underground facilities.