- Top of page
- 1. Introduction
- 2. Nearly Hydrostatic Pore Pressure at a Shallow Part
- 3. Nearly Lithostatic Pore Pressure at a Deep Part
- 4. Discussion
 Kato and Yoshida (2011) conducted a numerical simulation for understanding the mechanics of the 2011 Tohoku-oki earthquake. In this model, a strong asperity with higher effective normal stress was assumed at a shallower part of the plate interface. This shallow strong asperity controls the occurrence cycle of great earthquakes. The present paper discusses pore pressure distribution along the interface at the Pacific plate subducting beneath northern Honshu (Tohoku), Japan. Assuming that the permeability is exponentially dependent on effective stress and that the proportional constant drops to a lower value at a critical effective stress due to pore collapse, we obtained nearly hydrostatic pore pressure at a shallow part and nearly lithostatic pressure at a deep part of the plate interface. Assuming a different permeability model, in which increase of confining pressure has a larger effect than decrease of pore pressure, we obtained similar results. Such pore pressure distributions provide a possible generation mechanism for a shallow strong asperity.