太阳集团网tyc9728(百度)有限公司

Common artifacts existing in anisotropic elastic reverse time migration (ERTM) image are mainly cross-talk artifacts, false images and low-frequency noise. To address these problems, we propose a new elastic wave decomposition approach in vertical transversely isotropic (VTI) media, which decompose original elastic wavefield into up-/down-going P-wave and S-wave components for ameliorating imaging artifacts in ERTM. We first apply a space-domain VTI P/S wave-mode decomposition operator, reducing the cross-talk artifacts of ERTM image. Then, we derive the dispersion relation formulation of P-wave and S-wave which are used to construct Hilbert transformed operators in VTI media. For adapting to complex model, the first-order Taylor expansion around anisotropic parameter is applied to these derived P/S wave Hilbert transformed operators. We therefore present an up/down wavefield separation operator for VTI media that requires solving the wave equation only once, computing both the original wavefield and its Hilbert transform. This up/down going separated operator can be used to suppress false images and low-frequency noise of ERTM images. Finally we embed proposed up/down going wave separation into P/S wave-mode decomposition and develop a new elastic wave decomposing approach, which can efficiently improve the image quality in VTI ERTM. Simple and complex synthetic models demonstrate the effectiveness of our method.