"Tenpoku Seihou 3D"seismic data was acquired with the seismic vessel "SHIGEN" by METI in 2010. The survey area is approximately 770 sq. km. MOECO reprocessed the data in 2014 to improve the PSTM images obtained by JOGMEC in 2011. Much improvement was recognized in the reprocessing results. However, the PSTM images suggested very complicated subsurface geological structures in the survey area and the application of depth domain processing was required to confirm the structural features in detail. Then, MOECO decided to apply advanced depth imaging techniques to achieve further improvement of the deeper structural images. Under the cooperation with Paradigm Geophysical, both its advanced tomography velocity updating method and Paradigm Common Reflection Angle Migration (CRAM™) were selected as the most appropriate tools for this purpose. The input data were the preprocessed pre-stack gathers derived during MOECO's reprocessing in 2014. The resultant PSDM images are much clearer than the PSTM partly because the lateral seismic velocity changes were correctly handled in the processing and reflection signals were mapped to the right positions. Flexibility of the CRAM provides several different images through manipulations of decomposed wavefields in local angle domains. Those additional images could be useful to investigate structural features precisely. The interval velocity fields derived through the tomography iteration and residual move-out corrections followed are enough accurate to be utilized for further precise analyses.

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