Global Elastic Response Simulation

We pursue accurate numerical techniques to obtain theoretical seismic waves for realistic three dimensional (3-D) Earth models using Spectral-Element Method. We have tried to solve forward problem, that is, to calculate synthetic seismic waveform for fully 3-D Earth model. We introduce a heterogeneous region at Earth's core-mantle boundary by combining a small, strongly anomalous region to a large, weakly anomalous region. We calculate synthetic seismograms for this model and found that Sdiff phase, which is diffracted S-wave at core-mantle boundary, is followed by a significant postcursor. This is consistent with the anomalous Sdiff waveforms which sample beneath Hawaii. We use antipodal seismic observations to review the Earth's Core based on our synthetic seismograms. Our results imply that there may be anomalous structure at the Earth's inner core-outer core boundary.