4-D Imaging of Subsurface Changes with Coda Waves: Numerical Studies of 3-D Combined Sensitivity Kernels and Applications to the Mw 7.9, 2008 Wenchuan Earthquake

In the context of seismic monitoring, recent studies made successful use of seismic coda waves to image the lateral extent of medium changes. Locating the depth of the changes, however, remains a challenge. We use multiply scattered body- and surface-wave 3-D combined sensitivity kernels to address this problem. We show that we can locate velocity perturbations at depth with numerical data from elastic wave-field simulations in 3-D heterogeneous media. This procedure is then applied to assess the extent of the crustal damage due to the Mw 7.9, 2008 Wenchuan earthquake. We discuss the potential and limitations of our approach to retrieve the depth information of temporal changes occurring in heterogeneous structures.