Development mechanism and identification methods of subtle strike-slip faults in the Neogene-Quaternary of Bohai Sea

A large number of "subtle strike-slip faults" are developed in the Neogene-Quaternary strata in the Bohai Sea, which are difficult to identify in seismic data. These faults are steep, discontinuous, and have small fault throws. The existence of subtle faults could destroy the trap. In the process of oil and gas exploration, failure to identify subtle faults will lead to exploration failure. Therefore, it is urgent to re-understand subtle strike-slip faults from the perspective of fault development mechanism and guide their effective characterization. Based on the Neogene-Quaternary tectonic background of the Bohai Sea and three-dimensional seismic data, the development mechanism and identification method of subtle strike-slip faults were explored. Results show that the Neogene-Quaternary subtle strike-slip faults in the Bohai Sea are displacement-partitioned strike-slip faults developed under the oblique extensional tectonic background of pre-existing faults, and they are not directly controlled by basement strike-slip faults. There is a specific relationship among the angle α between the pre-existing boundary fault and the oblique extension direction, the angle θ between the pre-existing boundary fault and the oblique extension faults, and the probability P of displacement partitioning of strike-slip. This principle was used to effectively determine whether the subtle strike-slip fault was developed, and good application results were achieved. This study clarified the development mechanism and identification method of subtle strike-slip faults in the Neogene-Quaternary in the Bohai Sea, providing important guidance for oil and gas exploration.