Underground Cavity Detection Based on Elastodynamic Boundary Element and Topological Derivative Approaches

Abstract

Three-dimensional imaging of cavities embedded in a semi-infinite solid using elastic waves is a topic of intrinsic interest in a number of applications ranging from nondestructive material testing to oil prospecting and underground object detection. In situations when detailed mapping of buried objects (defense facilities, buried waste) is required and only a few measurements can be made, the use of surface discretization-based boundary integral equation (BIE) techniques provides the most direct link between the surface measurements and the buried geometrical objects. While such an approach is well established for acoustic problems [2], limited attention has so far been paid to the use of BIE methods in wave-based sensing of elastic solids. This communication reports the development of an analytical and computational framework for the identification of cavities in a semi-infinite solid from surface seismic measurements via an elastodynamic BIE method, as well as preliminary results on the investigation of the usefulness of the topological derivative (e.g. for choosing the initial guess).