Main faults and tectonic divisions in the South China Sea

Regional tectonic division is the foundation for studying tectonic evolution. The boundaries of regional tectonic division are mostly based on huge faults. Therefore, it is essential to study the major faults (belts) in one area before dividing structural units. After analyzing the main faults (or fault zones) in the South China Sea in plate tectonics theory, the tectonic division for the South China Sea was improved. The major faults (or fault zones) in the South China Sea include the first-order or primary fault zones that are characterized by subduction zones, collision zones, large thrust zones, and large strike-slip zones; the second-order faults that cut through the sedimentary basement and the upper crust, extending to the lower crust; and the third-order ones that run across sedimentary basement. The first-level tectonic unit in this region is the “South China Sea Subplate”, whose boundaries are mostly the first-order faults or sometimes the second-order ones. The second-level tectonic units include microplate, stepped fault zone, uplifted area, deep depression area or belt etc. The third-level tectonic units are are those divided within a microplate, including uplifted depression zone and microblock.