Elastic Full-Waveform Inversion Methodology for Shear-Wave Velocity Models

This document is a technical report detailing a methodology for updating shear-wave velocity (Vs) models using elastic full-waveform inversion (FWI) applied to multi-component ocean-bottom seismic data. The report outlines the challenges associated with inverting S waves for Vs updates, particularly the limitations of data acquisition and the reduced sensitivity of surface seismic to Vs. It presents a two-step workflow: the first step involves building a compressional velocity (Vp) model from hydrophone and vertical geophone data, while the second step reconstructs the Vs model using horizontal geophone data driven by converted waves. The methodology is demonstrated through a field application in the North Sea, showcasing improved PS reverse-time migration (RTM) imaging and better consistency with PP RTM results. The report compares the proposed elastic Vs FWI approach with existing methods, highlighting its advantages in terms of data processing and resolution in shallow environments.