Turning wave false image removal based on wavelength-dependent smoothing operator in reverse time migration
Tang Yongjie1,2, Song Guiqiao3, Liu Shaoyong1,2, Gu Hanming1,2, Yan Zhe1,2
1. Institute of Geophysics and Geomatics, China University of Geosciences(Wuhan), Wuhan, Hubei 430074, China; 2. Hubei Subsurface Multi-scale Imaging Key Laboratory, Wuhan, Hubei 430074, China; 3. Exploration & Development Department, SINOPEC, Beijing 100728, China
Abstract：The conventional reverse time migration (RTM) based on cross-correlation imaging conditions not only produces low-frequency artifacts,but also generates the false images of turning wave in the strong velocity gradient regions,and the false images cannot be removed by a simple Laplacian filter.In this paper,we introduce the imaging condition by separating up-going and down-going wavefields to analyze the causes of the false images in RTM and it does indicate that the false images of turning wave are generated by the cross-correlation of the up-going source and down-going receiver wavefields in the strong velocity gradient areas.In order to eliminate the false images and take into account the computational efficiency,we propose a false image removal method based on the wavelength-dependent smoothing operator.This method includes the wavelength effect which makes the propagation characteristics of wavefields in the strong velocity gradient areas more close to the propagation characteristics in the true velocity.Numerical experiments demonstrate that the proposed wavelength-dependent smoothing algorithm can suppress the turning wave false images and perform RTM efficiently under the classical imaging framework.
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