I am interested in the study of coda waves for monitoring purposes.
These waves are the result of a propagation through highly heterogeneous medium, such that multiple-scattering take place. Coda waves sample the medium very densely and become sensitive to perturbations of its mechanical or structural properties. Therefore, they are very useful to detect temporal changes within the medium.
Further research has led to development of sensitivity kernels which allow to locate where these changes occur. Still, more aspects are needed in order to get an accurate location in different types of medium.
Nevertheless, the development of such kernels would open new prospects in seismic imaging and monitoring applications.