Elastic wave-field inversion of reflection and transmission data

Elastic inversion of multioffset seismic data by wave-field fitting yields a maximum probability P-wave and S-wave velocity and density model of the Earth. Theoretically, the inversion accounts for all elastic waves. The different wave types tend to resolve different components of the Earth properties. Reflection data mainly resolve high wavenumbers, while transmission data mainly resolve low wavenumbers of the P-wave and S-wave velocity model. The inversion of reflection data (shot gathers) yields a result that looks like a prestack elastic migration but the meaning of the inverted data is not simply reflectivity: it is the P-wave and S-wave velocity perturbation. The inversion of transmission data (VSPs) yields a solution that contains useful interval velocity information and is comparable to an elastic diffraction tomography result. -Author