Coda Wave Interferometry
by Roel Snieder, WM Keck Distinguished Professor of Basic Exploration Science
Department of Geophysics, Colorado School of Mines

ABSTRACT
Multiple scattered waves are not very useful for deterministic imaging in complicated media because there is no known algorithm to construct such an image. Because multiple scattered waves have long wave-paths, these waves are very sensitive to small changes in the medium. Coda wave interferometry is a new technique that can be used to detect minute changes in a strongly scattering medium using changes in the multiple scattered waves over time. This technique is analogous to speckle pattern interferometry as used in optics, but takes advantage of the phase information in recorded waves. Because of its modest hardware requirements, coda wave interferometry has a large number of applications. These include geotechnical applications (dam-monitoring, tunnel monitoring), the evaluation of hazards (volcano and fault monitoring), non-destructive testing, and monitoring of hydrocarbon reservoirs.