Time-lapse Monitoring with Multiply Scattered Waves

Previous formulations of coda wave interferometry make it possible to assess the average change of the medium, but they do not allow for the spatial localization of this change (Snieder et al., 2002; Snieder, 2002). We present an approach for localizing temporal changes in the medium using strongly scattered waves, and test it with numerical models for 2D scalar waves. Using an integral representation for the diffuse wavefield, we derive an expression for the mean traveltime perturbation due to a small perturbation in the slowness. We validate the theory using synthetic seismograms calculated with a finite-difference algorithm. In general, for localized slowness perturbations, the theory predicts the mean traveltime change of the diffuse wavefield in a multiplescattering medium. The technique presented here can be used in many applications such as medical imaging, non-destructive testing, and reservoir monitoring, to infer temporal changes of the multiple-scattering medium.