Bending deformations of plates in the model of strong subduction earthquakes

Abstract

The model of elastic rebound of thin plates is considered to account for GPS-inferred surface deformation of plates during subduction earthquakes on the example of the M9 earthquake that occurred in Japan in 2011. Due to the fact that the oceanic plate moves together with a great mass of the convective mantle, it dips into the mantle at constant velocity all the time, both during the earthquakes and in the periods between them, although its coupling with the continental plate changes. The edge of the continental plate behaves as an elastic plate that permanently bends under the action of the friction force on contact with the diving oceanic plate. The bent plate unbends after the earthquake. This leads to its thrusting over the subducting oceanic plate. As a result, the island plate moves towards the ocean, its island part sinks, and the oceanic plate uplifts leading to a tsunami. The coordinates and magnitudes of the rise and subsidence correspond to the universal relations in the elastic plate model. The breaking of coupling of the continental plate with the submarine mountains and a basaltic plateau of the dipping plate is considered as a possible explanation of the anomalous properties of the strongest earthquakes. The main earthquake can be produced by partial destruction of a plateau or a large mountain. After this, the locked plates become free along a great area in an avalanche-like manner, and the friction of rest gives place to sliding friction.