On the importance of horizontal components in source-encoded elastic full-waveform inversion: Multicomponent ocean-bottom-node data

Elastic full-waveform inversion (EFWI) is a state-of-the-art seismic tomographic method. Recent advances in technology and instrumentation, combining crosstalk-free source-encoded FWI (SE-FWI) with multicomponent marine data acquisition using ocean-bottom nodes (OBNs), enable full-physics wave propagation and parameter inversion without the computational burden of traditional FWI. With OBN acquisition, P waves, S waves, and P-to-S conversions are recorded. It is not well understood to what extent adding horizontal components to SE-FWI improves the resolution of subsurface modeling. We assess their potential for the reconstruction of shear and compressional wave speeds (VP and VS) by using a synthetic data set modeled after a recently acquired OBN survey in the North Sea. We perform synthetic inversion tests to design suitable strategies that leverage the information recorded in the horizontal components of the data to improve the reconstructed model resolution laterally and in depth. We advocate for a hierarchical inversion approach to recover the elastic parameters. We exploit the P and P-to-S converted waves recorded on the horizontal components to robustly reconstruct both VP and VS. Adding horizontal components to the SE-FWI modeling workflow results in improved spatial resolution, enhanced depth coverage, and more accurate elastic wave speed estimates.