The velocity structure of the Yinggehai Basin and its hydrocarbon implication

Two profiles of refraction and wide-angle reflection were completed in the Yinggehai Basin using ocean bottom hydrophones (OBHs) as receiver. These pr ofiles reveal a low velocity layer (LVL) to the west of No. 1 Fault in the basin, with velocity of 3.0-3.5 km/s. Its upper interface lies at 3.5 km be low the sea bottom at the NE end of the profiles, and deepens southwestward to 4.6 km near the axis of the basin. It coincides with the top of a gas-b earing, high-pressure layer defined by well logging. This suggests that the LVL is a layer of less-compacted and gas-charged sediments. The tower inte rface of the LVL is about 9 km in depth. Sediments above the LVL have veloc ity varying from 2.0 to 4.1 km/s. The acoustic basement is found only east of No. 1 Fault, with velocity of 5.8-6.2 km/s. A NNW-SSE-running OBH seismi c profile across the Xisha Trough was completed on the same cruise. Moho an d other deep interfaces are clearly visible in the profile.