Main Controlling Factors of Imbricate Thrust Faults at the Frontal Edge of the Makran Accretionary Wedge–Insights from Physical Simulations

Abstract The frontal edge of the Makran accretionary wedge is characterized by the development of multiple imbricate thrust faults trending E-W and relatively parallel. However, the mechanisms underlying their formation and the factors controlling their development remain subjects of debate. This paper, based on seismic profile analysis, employs physical simulation experiments to establish a ‘wedge’ type subduction model. The study explores the influence of the initial wedge angle, horizontal sand layer thickness, and the presence or absence of a decollement layer on the structural styles of the thrust wedge. Experimental results indicate that as the initial wedge angle decreases from 11° to 8°, the lateral growth of the thrust wedge increases, whereas vertical growth diminishes. When the horizontal sand layer thickness is reduced from 4.5 cm to 3.0 cm, the spacing between the frontal thrusts decreases and the number of thrust faults increases. Both lateral and vertical growth are relatively reduced, resulting in a smaller thrust wedge. When a decollement layer is present, the structural style exhibits layered deformation. The decollement layer constrains the development of back thrusts and promotes the localized formation of frontal thrusts. In conclusion, the imbricate thrust faults at the frontal edge of the Makran accretionary wedge are primarily controlled by the characteristics of the wedge itself and the presence of the decollement layer.