Numerical simulation study on the zonation of Indosinian tectonic deformation and its characteristics in the Bohai Sea

The Indosinian movement laid the foundation for the formation of the present-day tectonic pattern in the Bohai Sea, which led to the formation of three major recoil zones within the Bohai Sea. The pre-existing faults and slip sheets within the Bohai Sea basement may have played an important role in this process, but the mechanism of how they affect the tectonic deformation and zonation characteristics of the Indochina in the Bohai Sea is not clear. In order to address these questions, this paper presents a detailed study of the tectonic deformation during the Indosinian period in the Bohai Sea based on seismic section data combined with the 2D thermodynamic numerical simulation code LaMEM. The simulation results reveal that, under the condition of pre-existing faults, when there is no slip layer in the basement or it is not stepped in the Bohai Sea, the three recoil centers will not be formed in the Bohai Sea; but when the slip layer in the basement is stepped in the southwestern part of the Bohai Sea, Bozhong Sag and Liaodong Sag, the stress is transmitted through the slip layer in the basement and the three recoil centers are formed in the Bohai Sea. The three recoil centers and lead to the development of large-scale recoil faults and fold deformation inside the Bohai Sea, which is in good agreement with the seismic profile. The numerical simulation results confirm that the pre-existing faults and slip layers in the basement are important factors controlling the tectonic zonation and tectonic deformation characteristics in the Bohai Sea. At the same time, the multi-reverse center evolution model also provides an important reference to explain the formation and evolution process of present-day Longmen Mountains and Sichuan Basin.