Applications of Waveform Inversion

Waveform inversion techniques aim to fit the entire seismic wavefield including those phases that conventional processing and migration seek to remove. Such methods have the potential to image the subsurface with significantly improved spatial resolution. The inversion in this paper uses a frequency-domain, finite-difference modeling method to solve the full acoustic wave equation, so high-order effects such as diffractions and multiple scattering are accounted for automatically. It is a local descent algorithm that refines a starting model iteratively to reduce the waveform misfit between observed and modeled data. Waveform inversion is applied to a number of synthetic models, including the complicated BP EAGE model. The results have demonstrated that waveform inversion has the potential to reconstruct high-resolution velocity structure. Some practical strategies were found to be critical in the application to real data. These strategies include: using a diving wave tomography model as a starting model; starting the inversion with the lowest available frequency; using complex-valued velocity to take care of undesired amplitude discrepancies; using complex-valued frequencies to simulate the damping of late arrivals; and handling surface-related multiples effectively.