Numerical Simulation Study on Recent Changes in Crustal Deformation and Seismicity in the Tokai Area, Central Japan

Abstract

Recently, Tada (1996) and Matsumura (2000) reported that crustal deformation rate and seismicity pattern have interestingly changed in the Tokai area, central Japan. We formulate recurring earthquake model in the Tokai area based on the rate- and state dependent frictional law derived from laboratory experiments of rock friction and on the location of a seismically locked region. Using the model parameters based on previous studies, we estimate the time when the next Tokai Earthquake will occur and the location of plate interface by fitting simulated calculation to observed data. Some of the results explain the recent decrease in the rate of uplift change especially at the three observational points.
We find out that the mechanism of microearthquakes is well explained by the rate change of stress field. The present model shows the vertical rotation of the axes of principal stresses and predicts the precursory change of seismic activity in the region, where the distance from the assumed trench along the relative plate motion direction is about 150 km, in the depth range of 10-20 km. The present seismicity with P axis almost horizontal will become more inactive several years before the occurrence of a great earthquake, and/or the direction of P axis rotates abruptly about 80 degrees so as to be orthogonal to plate interface.