Abstract:The secondary positioning of sensors is very important in the ocean bottom cable(OBC)seismic survey.In this paper,we discuss different shot point distributions,such as 3 shot point focus,2 shot point focus,3 shot points in line and 3 shot point triangle tetrahedral distributions.The computation and analysis results show that the first three distributions have a great influence on the sensor position accuracy even there are very small errors of the first arrival distance and the shot point coordinates.Moreover the first arrival distance error has much greater affects than the shot point coordinate errors.But with the tetrahedral distribution,both the first arrival distance error and the shot point coordinate errors has very small affects on the sensor position accuracy.Based on the model analysis results,the paper proposes a near tetrahedral secondary positioning method.Nearest tetrahedral combinations other than deviate combinations are chosen and calculated among many shot-receiver combinations on a large extent.Then the calculated results are statistically analyzed.Finally it is found that this approach can evidently increase sensor positioning accuracy.The method is not only simple but also computational efficient.Both model and offshore 3D examples show the validity and rationality of the method.