Abstract: The orientation and intensity of fracture are important information for the reservoir, however, the conventional compression wave (P) seismic data has limited resolution for fractures, while the shear wave splitting (SWS) caused by azimuth anisotropy in the converted seismic wave (PS) is helpful to characterize the strength and azimuth characteristics of fractures. In order to study the distribution characteristics of fractures in a study area of East China Sea, the converted shear wave information recorded in four-component submarine node (OBN) is used to extract SWS analysis. Firstly, the principle of SWS and the layer-stripped method are introduced in detail, then, the SWS analysis with the seismic data in the study area is carried out. The results show that in the shallow layer (0-3000ms), the time delay of fast and slow shear waves is 3-5ms, the average fracture direction is about 111-117°, the fracture similarity is as high as 80-90%, which indicate the fracture orientation is relatively concentrated. However, in the deeper layer, The distribution of fracture is rather complex, the time delay is about 6-8ms, and the main azimuth is concentrated at 119°, but the fracture similarity is low (less than 50%), which indicate the azimuth is not concentrated. The results show that NW-trending fractures are mainly developed in the shallow layer of the study area, and NW and NE-trending fractures are mainly developed in the deep layer, which is consistent with the fault development direction obtained from P results in the study area. The time delay gradually increased from shallow to deep part, indicating that the deeper the fracture development intensity. The time delay in the south of the study area was significantly higher than that in the north, indicating that the intensity of fracture in the south was higher than that in the north.

Key words: Shear wave splitting, OBN converted wave, Anisotropy, fracture characterization