Time reverse characterization of sources in heterogeneous media

Time reverse modeling of wave propagation in elastic media is applied to localize and characterize acoustic emission using a numerical concrete model. The aim is to transform a specific method within exploration geophysics to non-destructive testing. In contrast to previous standard localization techniques, no single event or first onset time identification is applied. The method is described and illustrated with synthetic data. Time reverse localization and characterization with limited knowledge of boundary values are feasible using the rotated staggered finite-difference method. Several imaging conditions are applied and compared to each other. We demonstrate the localization of two synchronous acoustic emissions with a limited number of sensors and using effective elastic properties. The imaging condition based on the maximum energy density is most indicative. Source characteristics can also be recovered. The goal is to apply our method to acoustic emissions measured during experiments carried out on concrete and reinforced concrete specimen. Several aspects of the described methodology can also be transferred back to exploration geophysics. (C) 2011 Elsevier Ltd. All rights reserved.