Abstract:

A three-dimensional finite-difference time-domain model for elastic waves in the ground has been developed and implemented on a massively parallel computer. The model is based on the three-dimensional equation of motion and the stress--strain relation, from which a first-order stress-velocity formulation is obtained. The boundary between the soil and the air is modeled as a free surface. A perfectly matched layer is implemented at the remaining grid edges to absorb the outward traveling waves. The numerical model has been developed as part of a project in which elastic and electromagnetic waves are used synergistically to detect buried landmines. The numerical model is being used to study the interaction of the elastic waves with the buried mines. To verify that the model accurately predicts the mine--wave interaction, the eigenfrequencies of various solid bars and plates are determined numerically and compared to analytical solutions. Currently, the model is being refined to incorporate loss within the bulk medium. Results will be shown for various landmines buried in both loss-free and lossy ground. [Work supported by ARO and ONR.]