Abstract: The Yinggehai Basin is an important basin in the northwestern South China Sea where wealthy gas led to fuzzy reflection zones in the conventional P-wave seismic reflection record. Ocean bottom cable ( OBC ) survey was used as a new method to reveal the gas-bearing characteristics of the Yinggehai Basin. Multi-component OBC can provide more information than other existing methods. Different from the surface observation method, its shots and receivers are deployed several meters under the surface and on the sea-bottom, respectively; therefore, the wave ray-paths are highly asymmetric. As a result, conventional seismic data processing methods cannot be directly used to the OBC record. A primary preprocessing procedure is altitude datuming for the shots or receivers to make the shots and receivers in the same datum. The most-often used datuming methods include static correction and Kirchhoff wave field extrapolation. In this paper, Kirchhoff wave field extrapolation is used to compare with the static correction method for datuming of the OBC record collected from the Yinggehai Basin. The resultant velocity analysis and wave fields show that the static correction causes significant velocity deviation, more than 10 percent in the uppermost layer, whereas Kirchhoff wave field extrapolation maintains correct velocity for all layers, and obtain correct wave field to the target datum.

Key words: ocean bottom cable record, datuming, Kirchhoff integration, wave field extrapolation;static correction