3D elastic migration with topography based on spectral-element and adjoint methods

Although wave equation based migration techniques, such as Reverse Time Migration (RTM), have been popular for years, the acoustic approximation is still applied frequently. Even when considering anisotropic behavior, modifications to the acoustic wave equation are invoked to facilitate changes in wavespeed along different directions. In a classical marine survey, seismic waves are generated in the water layer and observations are recorded in the form of pressure fluctuations. In that case, using a purely acoustic wave equation is a reasonable assumption, since conversions between compressional and shear motions along the ocean bottom are weak. However, with the availability of Ocean Bottom Cables (OBCs) or in land surveys, shear waves do play an important role. On one hand, incorporating elastic information in imaging may enhance the coherence of arrivals and thus provide better images. On the other hand, recorded shear signals might contaminate the image if falsely interpreted as reflected compressional waves. Following these considerations, we carry out a 3D elastic experiment investigating proper imaging conditions for elastic migration.