Elastic reverse-time migration of multi-component data has the potential to directly image steeply-dipping fault zones for geothermal exploration. However, this imaging method requires an accurate velocity model. Elastic-waveform inversion is a promising tool for velocity estimation. Because of the ill-posedness of elastic-waveform inversion, it is a great challenge to accurately obtain velocity estimation, particularly in the deep regions and fault zones. To improve velocity model building, we develop an elastic-waveform inversion method with an edge-guided modified total-variation regularization scheme to improve the inversion accuracy and robustness, particularly for sharp interfaces and steeply-dipping fault zones. The new regularization scheme incorporates the edge information into elastic-waveform inversion. The edge information of subsurface interfaces is obtained iteratively using migration imaging during elastic-waveform inversion. We validate the improved capability of our new elastic-waveform inversion method using synthetic seismic data for a Soda Lake geothermal model containing several steeply-dipping fault zones. The improved velocity model could significantly improve direct imaging of steeply-dipping fault zones.

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