Next-Generation Imaging Technique for Underground Object Detection

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

The aim of this project is to develop an advanced computational and experimental basis for expedient 3D imaging of subterranean objects using elastic (i.e. seismic) waves. In contrast to existing three-dimensional seismic analyses that require full volume discretization of the underground domain, the proposed imaging technology revolves around an elastodynamic Boundary Integral Equation (BIE) method so that only the outline of a hidden object is rendered. This boundary-only sensing approach, which offers formidable computational savings, has its origins in radar and sonar technologies, but has been largely unexplored in the context of seismic surveys. Aimed at bridging such gap, the first stage of this research is focused on elevating the prototype BIE imaging technique as to increase its robustness, account for a wider class of subterranean conditions, and deal with the detrimental effects of experimental and modeling errors. The experimental phase of this project aims to implement the new sensing technology into a compact testing setup that involves a vibratory seismic source and a surface array of triaxial motion sensors. The research efforts include 1) generalization of the recent findings in acoustics and structural shape optimization to develop a rapid ground-probing technique and thus furnish a reliable initial guess required for the high-fidelity BIE imaging; 2) extensions of the method to deal with noise-polluted measurements and multi-layered geological deposits; 3) synthesis of the computational developments for a robust, yet expedient approach to 3D seismic sensing; 4) small-scale implementation of the method to identify obstacles buried in a sand bin, and 5) a field effort aimed at imaging an existing, on-campus underground facility. The foregoing research program will be complemented with a continuing effort to foster the growing use of non-destructive testing in civil engineering. Potential applications of the new sensing technology include rapid detection of underground facilities and unexploded ordnances; cost-effective mapping of subterranean infrastructure in urban areas, and non-invasive delineation of buried waste. The need for fast and economic 3D seismic imaging in these and other areas is especially pronounced in situations where electromagnetic surveys may be inadequate due to their limited resolution and depth of penetration