Correcting Fault Shadows – a Case Study Comparison of Fault-Constrained Tomography and Time-Lag Full-Waveform Inversion

Solving fault shadow imaging problems has been a long-existing topic when heavy faults are present and the seismic imaging underneath is distorted. With full-waveform inversion (FWI), they are usually less of a concern when their depths are within diving wave penetration. However, beyond diving wave penetration, we have to rely on reflection energy, either by various tomographic methods or reflection FWI, both of which require special considerations in order to effectively resolve small-scale velocity anomalies associated with faults. In this paper, we present applications of fault-constrained tomography (FCT) and Time-lag FWI (TLFWI) with a weighted tomographic term for deep fault imaging using a streamer dataset with limited offsets from the South China Sea. Our learnings show FCT heavily hinges on high-quality common image gather (CIG) and fault picking. With a weighting factor to promote the tomographic term from reflection energies, the TLFWI workflow successfully corrected fault shadows and demonstrated advantages over FCT for resolving velocity anomalies in areas of complex faults.