Plate bending and in-plate stress variation caused by seamount subduction

Abstract:

Seamount loading can result in lithosphere flexures which has been well-studied. However, the plate bending and corresponding in-plate stress caused by seamount subduction is rarely investigated. Understanding the key factors controlling the interactive processes of plate bending and seamount subduction is of major significance to study the dynamics of the subduction zones. Here we conducted a systematic analysis of the bending deformation of subducting plate with a seamount close to the trench using a thin plate model, assuming the seamount plays a role to thicken the effective elastic thickness (T_e). We carried out dozens of models to study the effect of the distance between seamount and trench on plate bending deformation and in-plate stress with variable T_e. We found that when distance between seamount and trench is smaller than 140 - 220 km (corresponding T_e of 20 - 50 km), seamount start to affect the bending deformation and in-plate stress. The seamount make bending deformation smaller and the in-plate stress concentrating in an area in front of the seamount. The stress-concentration area is more likely to have earthquakes. The distance between the area and the seamount changes from ~20 to ~30 km. This model could applicable to the northern Ryukyu Trench where the high-angle normal faults and corresponding earthquakes are observed at a distance of ~25 km in front of an oceanic plateau.