The 2011 earthquake off the Pacific coast of Tohoku (Tohoku-oki earthquake) was one of the most destructive events in Japanese history, and has drawn attention from geoscientists all over the world. Although many papers dealing with it have been published, its geophysical causes and effects are still highly mysterious. This gap exists mainly because the basic properties and physical conditions of the media that constitute the island-arc crust and mantle are poorly understood: trying to make predictive models about them is like weather forecasting without knowing atmospheric pressure and humidity. The main purposes of this research project are to determine the absolute values of crustal stresses, to provide a unified view of deformation in the Japanese islands, and to clarify properties of island-arc crust and mantle, such as viscosity and frictional coefficients along major faults, about all of which little is known. The intended result is a comprehensive description of the various geophysical phenomena that have occurred after the Tohoku-oki earthquake.
The basic approach of this research project is:
(A) to estimate absolute values of stress, strain, and strain rate from observation data;
(B) to estimate properties of the media including crustal fluids and their spatial and temporal changes from field observations and laboratory experiments; and
(C) to construct numerical models based on the above knowledge, reproduce the observations, and validate these models.
The research is divided among six research groups who work on their respective themes under the direction of the administrative group:
The following two research directions comprise the main contents of this project.
(1) Understanding of the stress field:
We will estimate the absolute value of stresses using a seismological method, and investigate the properties of the media that govern them.
(2) Understanding of the strain-rate field:
We will estimate short- and long-term strain and strain-rate fields using geodetic, geological, and geomorphological methods, and investigate the properties of the media that govern them.
We take advantage of the unprecedented large changes in stress and strain caused by the Tohoku-oki earthquake to try to resolve these problems that have been difficult to answer.