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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy<br />

(S) - <strong>IASPEI</strong> - International Association of Seismology and Physics of the Earth's<br />

Interior<br />

JSS002 Poster presentation 1798<br />

An Integrated Numerical Simulation for Tsunami and Seismic Wave<br />

Propagation Generated by Subduction-Zone Large Earthquakes<br />

Dr. Tatsuhiko Saito<br />

Earthquake Research Institute the University of Tokyo <strong>IASPEI</strong><br />

Takashi Furumura<br />

We develop an integrated simulation model for tsunami and seismic wave propagation to make accurate<br />

prediction of tsunami disasters caused by subduction-zone earthquakes. We employ a 3D FDM<br />

simulation technique for evaluating the spatial and temporal deformation of sea floor caused by the<br />

earthquake, and the resultant vertical movement of the sea-floor deformation is used as tsunami source<br />

model. Unlike the conventional tsunami simulation models that usually assume a simple half-space<br />

subsurface structure and calculates static deformation of sea-floor, our new model includes the effects<br />

of 3D heterogeneous structure near the source region and dynamic deformation process of sea floor. In<br />

order to demonstrate the effectiveness of our new model, we conducted a seismic and tsunami<br />

simulation for the 1944 Tonankai earthquake (Mw8.1) that occurred in the Nankai Trough, Japan. At<br />

first, we calculated the seismic wavefield using a detail source rupture model for the earthquake and a<br />

3D heterogeneous structure of the Nankai-Trough subduction zone. This model includes detail structure<br />

of the subducting plate and low-velocity oceanic sediment at the top of the plate. The FDM simulation<br />

for seismic wave takes about 100 minutes on the Earth simulator supercomputer using 24 nodes<br />

(192CPUs) of processors and 290GB of computer memory for evaluating seismic wave propagation of<br />

200 s. Then, using the simulation results as tsunami source, we evaluate the tsunami propagation by<br />

FDM based on the linear long-wave theory. The tsunami simulation was conducted on a cluster of 16<br />

AMD Opteron processors, which takes about 10 minutes for calculating 60 minutes of tsunami<br />

propagation. The seismic simulation using 3D structural model shows large deformation of the seafloor<br />

in localized region compared with that derived assuming homogeneous half-space structure. This is<br />

because, in inhomogeneous subsurface structure, the seismic strain is accumulated in small elasticity<br />

portion. As a result, tsunami wave of our simulation has larger maximum amplitude than that calculated<br />

with homogeneous half-space medium. Also, the deformation of sea floor associated with the Rayleigh<br />

waves also excites weak tsunami in the direction of fault rupture propagation as a forerunner of major<br />

tsunami signals which might give some information for tsunami early warning system.<br />

Keywords: tsunami, seismic, simulation

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