Accurate Velocity Estimation for Steep Fault Zones Using Full-Waveform Inversion With Edge-Guided Regularization

Abstract

Reverse-time migration has the potential to directly image steeply-dipping fault zones. However, it requires an accurate velocity model. Full-waveform inversion is a promising tool for velocity estimation. Because of the ill-posedness of full-waveform inversion, it is a great challenge to accurately obtain velocity estimation, particularly in the deep regions and fault zones. To improve velocity estimation, we develop a full-waveform inversion method with an edge-guided modified total-variation regularization scheme to improve the inversion accuracy and robustness, particularly for steeply-dipping fault zones with widths of much smaller than the seismic wavelength. The new regularization scheme incorporates the edge information into waveform inversion. The edge information of subsurface interfaces is obtained iteratively using migration imaging during waveform inversion. Seismic migration is a robust tool for subsurface imaging. Our new full-waveform inversion takes advantage of the robustness of migration imaging to improve velocity estimation. We validate the improved capability of our new full-waveform inversion method using synthetic seismic data for a complex model containing several steeply-dipping fault zones. Our inversion results are much better than those produced without using edge-guided regularization. Full-waveform inversion with an edge-guided modified total-variation regularization scheme has the potential to estimate velocities within steep fault zones, which would significantly improve direct imaging of these faults.