Effect of subduction of seamounts on tectonic deformation of the crust surface: Insights from discrete numerical simulations

2D discrete element numerical experiments are used to investigate the effect of seamounts subduction on shallow surface tectonic deformation in this paper. It is proved that the interaction between seamounts subduction along the accretionary margins and rough seabed topography give the unique stratigraphic evolution variations: (1) The seamounts develop large offset thrust faults, which are characterized by complex deformation, even with curling in shape; Reversed ridges are located directly above the seamounts, representing the area with the most intense deformation. (2) Seamounts subduction leads to more complex and irregular shapes of the wedge. Seamounts significantly hinder the lateral extension of the wedge. By conducting comparative experiments with different dipping angles, it was proved that the wedge-shaped body with a dipping angle of 35 degrees has a larger dipping angle than the Marianas-type subduction zone. In this case, the subducting plate separates from the overlying plate, and a large amount of ocean sediments is eroded and subducted, thus forming a narrow accretion wedge. In contrast, the accretion wedge formed by the wedge-shaped geometry at a dipping angle of 25 degrees is wider and lower in elevation, with a slope slightly lower than that of the accretion wedge formed by the wedge with a dipping angle of 35 degrees that is composed of oceanic islands. This phenomenon corresponds to the Chile-type subduction zone, where the smaller dipping angle causes the subducting plate and overlying plate to be closely coupled, which is not conducive to the erosion and subduction of ocean sediments, thus allowing for the formation of a wide accretion wedge; (3) Seamounts subduction can lead to the emergence of high- velocity zones at the Earth's surface and contribute to the upward transport of deep subducted sediments to shallow levels. The resultant variations and related fractures are conducive to enhancing the coupling degree across plate boundaries and augmenting the possibility of major earthquakes in this context. This indicates the necessity of reevaluating the interaction between seamounts and the crustal surface, and holds enlightenment significance for assessing the hazards of seamount subduction in accretionary margins.