Locating a weak change using diffuse waves (LOCADIFF) : theoretical approach and inversion procedure

TL;DR

LOCADIFF is a theoretical method using diffuse wave analysis and maximum likelihood to precisely locate weak changes in heterogeneous media, with potential for practical monitoring applications.

Contribution

This paper introduces LOCADIFF, a novel theoretical approach combining diffusive wave modeling and inversion for detecting weak changes in media.

Findings

Change can be located within a few wavelengths.

Effective scattering cross-section can be retrieved.

Method's precision depends on source-receiver pairs and model accuracy.

Abstract

We describe a time-resolved monitoring technique for heterogeneous media. Our approach is based on the spatial variations of the cross-coherence of coda waveforms acquired at fixed positions but at different dates. To locate and characterize a weak change that occurred between successive acquisitions, we use a maximum likelihood approach combined with a diffusive propagation model. We illustrate this technique, called LOCADIFF, with numerical simulations. In several illustrative examples, we show that the change can be located with a precision of a few wavelengths and its effective scattering cross-section can be retrieved. The precision of the method depending on the number of source receiver pairs, time window in the coda, and errors in the propagation model is investigated. Limits of applications of the technique to real-world experiments are discussed.