Simulation Study On The Influencing Factors Of Plate Wedge Subduction Deformation Style

It is necessary to clarify the development characteristics and deformation mechanism of the Makran accretionary wedge in northwestern Indian Ocean to better guide the exploration of gas hydrate deposits.In this study,typical structures such as deep imbricate thrust faults,shallow small normal faults,wedge-shaped piggyback basins,mud diapirs with fuzzy and disorderly reflection characteristics,décollement with a northward tilt of 1°–2° and large seamounts are identified through seismic data interpretation.By making the faults plane distribution map and tectonic evolution sections,it is considered that the shrinkage and shrinkage rate of the S–N seismic sections in the study area from west to east are decreasing.There is a ’two-layout structure’ in the longitudinal direction of the S–N seismic sections,that is,the combination of deep thrust faults and shallow normal faults.There is a ’three-layout structure’ in the longitudinal direction of the E–W seismic profile,that is,the combination of the basement high-angle normal faults,deep thrust faults and shallow normal faults.Mud diapirs and seamounts in the east of Makran accretionary wedge affect the development of thrust faults,resulting in poor continuity and segmentation of faults in the plane distribution.The development process of accretionary wedge is simulated by structural physical simulation experiment.According to the comprehensive plane simulation and section slice results,it is concluded that the plastic décollement layer at the bottom of the Markland accretionary wedge has a great influence on the faults development styles and interval,the thrust imbricate faults of the Makran accretionary wedge develop ahead of the thrust front.The shallow normal faults are formed by the rapid uplift of the lower fault-related folds,resulting in tensile fracture in the upper part or collapse of the upper strata.The thrust fault provides a good migration channel for the upwelling of the plastic materials at the bottom.The plastic materials upwelling along the thrust faults and accumulate on its hanging wall to form diapir structures.The plastic materials at the bottom of the area near the trench upwell sharply,resulting in many large-scale diapir structures in the mid-slope and upper-slope of the accretionary wedge.According to the interpretation of seismic sections,the Makran accretionary wedge develops various BSR types,such as accretionary wedge type,ridge type,basin margin type,buried anticline type and slump type,indicating that there are a variety of structurally controlled gas hydrate deposits in the study area.