Modeling of global seismic wave propagation on the Earth Simulator

We use the Earth Simulator to model seismic wave propagation resulting from large earthquakes on a global scale. Simulations are conducted based upon the spectral-element method, a high-degree finiteelement technique. We include the full complexity of the Earth, i.e., a three-dimensional seismic wave velocity and density structure, a 3-D crustal model, the elliptical figure of the Earth as well as topography and bathymetry. We use 507 nodes of the Earth Simulator (4056 processors) and model the three dimensional Earth with 13.7 billion grid points. A total of 7 terabytes of memory is needed. We have reached a vectorization ratio of 99.3%, and attained a total performance of 10 teraflops (32% of the peak performance). The very high resolution of the mesh allows us to calculate theoretical seismic waves for realistic fully three-dimensional Earth model, which are accurate at periods of 3.5 seconds and longer. We have modeled seismic waves generated by recent large earthquakes and show the importance of including three-dimensional structure in the seismic wave simulation. These theoretical seismograms calculated for fully three-dimensional Earth models should improve our understanding of earthquake source mechanisms and the Earth dynamics.