Wavelet stretch correction for reverse-time migration
Yang Jiajia1,2, He Bingshou1,2, Chen Ting1,2
1. Key Laboratory of Submarine Geosciences and Prospecting Techniques, Ministry of Education, Qingdao, Shandong 266100, China;
2. Ocean University of China, Qingdao, Shandong 266100, China
Abstract:Wavelet stretch effects of large reflection angle affect seriously the image resolution of prestack reverse-time migration. According to Tygel's study, wavelet is stretched with the increase of reflection angle and local reflector dip in the vertical direction. We develop a wavelet stretch correction method after extrapolation of reverse-time migration and before applying imaging condition. First we extract wavelets in imaging time at each spatial grid point of both source wavefield and receiver wavefield, then shrink the extracted wavelets, and finally apply normalized wavefield separation cross-correlation imaging condition, and obtain stretch correction results. This method does not change the amplitude and phase of imaging. Reflect angle and local reflector dip used for shrink operation are calculated from Poynting vector of seismic wavefield. Numerical examples show that this proposed method can correct wavelet stretch effects caused by large reflection angle, improve the image quality of prestack reverse-time migration, and provide high resolution data for AVA/AVO analysis.
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