Prestack elastic generalized-screen migration for multicomponent data

초록

An efficient prestack depth migration method based on the elastic one-way wave equation was developed using an improved elastic generalized-screen propagator, which effectively describes the behavior of elastic waves with mode conversion at the interfaces and efficiently computes wave propagation in media with lateral velocity variations. The elastic propagator presented in this study was improved from the elastic generalized-screen propagator. Several terms of the vertical slowness right symbol with orders are corrected from the original formulation, and the vertical slowness operator in the propagator was expanded up to the 2nd order which yields a more accurate approximation. In each screen propagation step, the multicomponent wavefields are automatically separated into the P and S wavefields by the P-S decomposition operator included in the elastic generalized-screen propagator. This process facilitates the imaging of the P and S waves separately without any additional P and S separation process after the wavefield extrapolation. Impulse response tests of the improved elastic generalized-screen propagator in a uniform-property medium proved that propagation accuracy increases with order, even when large medium perturbations are assigned. Migration tests using the developed algorithm on a simple layered model and two complex models (the SEG/EAGE salt and elastic Marmousi-2 model) demonstrated the functional advantages and capabilities of the algorithm compared with elastic migration using the scalar wave equation.

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