Finite-Difference Algorithm for 3D Orthorhombic Elastic Wave Propagation

Session: Explosion Seismology Advances [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Most commonly for numerical simulations, earth materials are treated as an isotropic medium for the sake of simplicity and due to weakness of anisotropy in the far field. However, most earth materials are seismically anisotropic. In specific circumstances, such as in shales, tectonic fabrics or oriented fractures, the use of anisotropic simulations is necessary in order to accurately model the earth. One approach is to model the material as an orthorhombic medium. An orthorhombic medium is characterized by three mutually orthogonal symmetry planes comprising a dense system of vertically-aligned microfractures superimposed on a finely-layered horizontal geology, which can be reduced to an elastic stress-strain constitutive relationship containing nine independent moduli comprising a set of nine, coupled, first-order, linear, inhomogeneous partial differential equations. A new massively parallel 3-D full seismic waveform simulation algorithm within the principle coordinate system of an orthorhombic material, which is a specific form of anisotropy common in layered, fractured media, has been developed.

This finite difference (FD) code is used to support the modeling component of the Source Physics Experiment (SPE), a series underground chemical explosions at the Nevada National Security Site. The data from the experiments are used to help determine event signatures that vary depending on geology, yield and depth of burial. An improved anisotropic model has been developed using observations from the SPE Phase I experiments and stochastic models to mimic the scattering seen in the data. The results of the modeling are presented.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2020-0215 A

Presenting Author: Richard P. Jensen

Authors