Imaging of near-surface heterogeneities by scattered elastic waves

We have developed an elastic reverse time migration (RTM) approach for imaging near-surface heterogeneities, such as karst features, using scattered waves (e.g., body to P-, S-, and surface waves). Knowledge of location and strength of the scatterers helps in seismic imaging, survey planning, and geotechnical site characterization. To model seismic wave propagation for RTM, we use an elastic staggered-grid finite-difference scheme. The scattered body-to-surface waves provide optimal illumination and wavenumber coverage of the near surface as they travel horizontally along the free surface. We tested the elastic RTM approach on synthetic data simulated using a finite-difference solver and found it to be robust.