Abstract:

Three types of positive inversion structures are found in the North Sag of South Yellow Sea Basin with interpretation of reprocessed 2D seismic data. They are classified into three types: the reversed fault type in the central and southern part, the transpressional type in the eastern part and the compressional fold type in the northern part. Where the inversion structures located was depended on the different tectonic positions. Based on the integrated analysis of balance sections of the typical seismic profiles and the regional tectonic background, it was considered that three episodic positive inversions had happened in the North Sag at least, which were influenced by the change of the subduction angle and rate from the Pacific plate to the Eurasian continent during the Cenozoic period. After the Sanduo Formation deposited, the subduction direction of the Pacific plate changed from NW to SWW and the subduction rate increased twice nearly. This change caused the most intensely positive inversion episode of the North Sag because of the SWW compressional force from the Pacific plate, which presented the strongest reversely faulting and erosion. Meanwhile, the excessively positive inversion may not be good for the hydrocarbon accumulation in the North Sag.

Key words: positive inversion, structure style, tectonic evolution, south Yellow Sea Basin