The sensitivity of converted-phase extended images to P- and S-wavespeed variations

Abstract

Converted-phase (CP) imaging produces high resolution images and can be used effectively for updating both P- and Swave speed models with an optimization scheme that is formulated in the extended image domain. This optimization is referred to as source-independent converted-phase WEMVA (SICP-WEMVA). However, the convergence of the optimization scheme depends on the selection of parameters and the formulation of the objective functions and their gradients. In this study, we investigate the sensitivity of the extended images for SICP-WEMVA to the domain where the objective function is formulated. We derive analytically the behavior of the seismic energy (i.e., seismic moveout) in the extended horizontal and vertical subsurface space-lag images as a function of P- and S-wave speed variations, and compare them with numerical results. The results of the moveout analysis demonstrate that the extended vertical subsurface space-lag images have higher sensitivity to the background P- and Swave speed variations than the horizontally extended images and thus may have significant implications on the resolution and convergence of the SICP-WEMVA.