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Detecting and Estimating Anisotropy Errors Using Full Waveform Inversion and Ray-based Tomography
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 76th EAGE Conference and Exhibition 2014, Jun 2014, Volume 2014, p.1 - 5
Abstract
Full waveform inversion (FWI) is widely used to obtain high-resolution subsurface parameters using diving and refracted waves in a wide range of acquisition scenarios. Frequently, however, quality checks in the image domain using conventional Pre-Stack Depth Migration (PSDM) indicate that the curvature of the common image point (CIP) gathers does not systematically improve compared to ray-based reflection tomography (RAY) counterparts.
We investigate the drivers for the inconsistency between the two approaches. The transmission-based FWI scheme relies heavily on wide angle arrivals, while reflection tomography relies on the near angle reflections due to impedance contrasts. Therefore, these two approaches provide complementary information of the Earth, and we try to exploit this view to evaluate the anisotropy parameters and obtain better estimates of and V_0, assuming knowledge of δ. We present the challenges of decoupling these parameters using a canonical example. We also propose a heuristic approach to estimate the anisotropy and velocity errors to simultaneously minimize the cost functions of FWI and RAY. We apply the workflow to the Marmousi data set and demonstrate that we can, to some extent, recover long wave components of the anisotropy. A field data example will be shown in the presentation itself.