Long-Period Ground Motion Simulation of 2004 off the KII Peninsula Earthquakes and Prediction of Future M8 Class Earthquakes along Nankai Trough Subduction Zone, South of Japan Island

Abstract eng:
We simulate long-period ground motions of observed Magnitude 7 class earthquake and predict those of future Magnitude 8 class large subduction earthquakes along Nankai Trough, south off Japanese archipelago. The numerical simulations are performed by a large-scale finite element method considering three-dimensional subsurface structure including both of propagation pass structure and large-scale sedimentary basin structure of Kanto plain on which Tokyo metropolitan is located. To verify the three-dimensional subsurface ground model, we simulate the 2004 off the Kii peninsula earthquake that occurred near Nankai Trough. The soft layer of the sedimentary wedge along Nankai trough has the effect to elongate the duration of ground motion and lessen the amplitude. We simulated the ground motion of the Tokai-Tonankai coupled earthquake. Long period ground motion reaches Kanto plain about 130 seconds after the rupture starts. The principal motion continues more than 4 minutes. The model shown in this study still has a limitation to underestimate the amplified ground motions in the Kanto plain. It is necessary to adjust velocity structure and Q value to obtain a better model.

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