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Building velocity models and Imaging subsurface with plane wave data

By Zeyu Zhao (UTIG)
Fri, September 8, 10:30am - 11:30am

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Host: Mrinal Sen

Velocity building and seismic imaging is critical in providing the image of the Earth's subsurface, and they play important roles in hydrocarbon explorations. Obtaining high resolution images with accurate reflectivities and accurate positions of subsurface structures is the goal for exploration geophysicists. Full waveform inversion (FWI) and reverse time migration (RTM), which seek the solution from the two-way wave equation, can accurately resolve all wavefield propagation phenomena. In geologically complex regions, FWI and RTM have been proven to outperform other inversion methods and imaging methods in correctly revealing the subsurface structures. Here, we introduce a new imaging principle that utilizes plane wave data to obtain subsurface structures. We employ the newly proposed imaging principle in FWI and RTM on plane wave data. Because the propagation of a plane wave obeys the Snell's law, plane waves with large incident angles at the surface would have relatively shallow penetration depth. We develop a strategy to implement FWI in a layer-stripping fashion. In the proposed FWI, we start the inversion using plane waves that have large incident angles to retrieve velocity information at the top of a model. Plane waves with relatively small incident angles are then included into the inversion process to recover velocities in the deep part of a model. After obtaining a reasonable velocity model, we implement RTM using plane wave data. Because plane waves can be used to image subsurface according to their propagation angles, we propose an imaging method to recover subsurface interfaces with different dip angles. It makes the plane wave RTM a target-oriented seismic imaging method. We show the effectiveness of proposed methods using several numerical examples.