Imaging Steeply Dipping Faults Using Angle-Controlled Decoupled Elastic Reverse-Time Migration of Multicomponent Seismic Data

High-angle and steeply dipping faults are important for geothermal fluid flow and production. However, imaging such faults is challenging for conventional seismic imaging methods using acoustic waves because of the limited illumination of compressional waves. We develop a novel imaging method to use elastic waves including both compressional-to-compressional (P-P) waves and compressional-to-shear (P-to-S) converted waves to image the high-angle faults. P-S converted waves provide additional seismic illumination for high-angle faults because they have smaller reflection angles than those of the P-P reflection waves at interfaces. Our new imaging method employs the decoupled wave equations in the context of elastic reverse-time migration (ERTM) to perform imaging using both P-P and P-S waves. Our decoupled ERTM does not require the polarity correction of S waves. In addition, we use the Poynting vector, measuring the wave propagation direction by computing the wave energy flux to control the image dip angles, thus improving the ability to image high-angle faults. Based on the angle-controlled P-P and P-S images, we further enhance the structural images of high-angle faults by extracting the significant structures that coexist in both P-P and P-S images. We apply our angle-controlled decoupled ERTM angle-controlled decoupled elastic reverse-time migration (ADEM) to synthetic multicomponent seismic data for a simple layer model with two vertical faults and a modified Marmousi2 model with artificially embedded vertical faults. Our numerical results demonstrate that our ADEM method can effectively image high-angle faults in complex structures using both P-P and P-S waves.