An integrated inversion of seismic refraction and reflection data using combined wave-equation tomography and full waveform inversion

We have developed an integrated method to obtain highresolution subsurface elastic parameters using combined wave equation tomography (WET) and full waveform inversion (FWI). Both refraction and reflection data are used. During parameterization, long wavelength and short wavelength structures are separated and mapped into velocity and density to account for kinematics and dynamics, respectively. Full wavefield modeling is used to compute synthetic data that include all reflection and refraction arrivals. To better constrain the reflection amplitude, the near offset data are first inverted using FWI where all the model perturbations are mapped into density. The short wavelength density structure is then converted into vertical travel time domain where it is independent of long wavelength velocity model. The WET is applied to both reflection and refraction data. As long wavelength structure (velocity) is updated, short wavelength structure is converted back into depth domain for wavefield computation. Finally FWI is applied all the data to retrieve short wavelength structures with resolution up to a quarter wavelength. The method is applied to two synthetic examples; our results shows that one can recover detailed velocity information starting from a model far from the final model.