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Abstract

We have performed global seismic wave propagation calculations using the spectral element method, which is a type of finite element method, with an accuracy of 1.6 seconds by using the Earth Simulator (ES4) system. In this calculation, the theoretical seismic waveform propagating globe was calculated by dividing it into 244.7 billion grid points. The parameters NEX and NPROC indicating the division of the spectral element method in this case are 2656 and 83, respectively, and the total number of cores used in the calculation is 41,334. For this scale of calculation, it took about 30 minutes CPU time to calculate the mesh and 4 hours 40 minutes CPU time to calculate the theoretical seismic waveform for 23 minutes. The size of the mesh is about 41 Tbyte. The Earth's internal structure model used in the calculation is transversly isotropic PREM (Dziewonski and Anderson, 1981) for the radial symmetric structure model, and s362ani (Kustowski et al., 2006) for the mantle three-dimensional structure. We analyse the basal outer core boundary (BOC) with antipodal waveform data in the distance range 179.0°–180° to test the hypothesis whether propagation at the BOC is commensurate with diffraction and/or refraction. We try thin LVZ models. Synthetic modeling of the thin, low velocity structures requires higher resolution (1.6 sec) parametrization to achieve necessary detail. We synthesized the antipodal data at the Qiongzhong (QIZ) station in China due to the April 17, 2009 earthquake in northern Chile (Mw6.1). We discuss the results in our presenation.