Comparative analysis of the characteristics of global seismic wave propagation excited by the Mw9.0 Tohoku earthquake using numerical simulation

Abstract

Giant earthquakes generate rich signals that can be used to explore the characteristics of the hierarchical structure of the Earth’s interior associated with the eigenfrequencies of the Earth. We employ the spectral element method, incorporated with large-scale parallel computing technology, to investigate the characteristics of global seismic wave propagation excited by the 2011 Mw9.0 Tohoku earthquake. The transversely isotropic PREM model is employed as a prototype of our numerical global Earth model. Topographic data and the effect of the oceans are taken into consideration. Wave propagation processes are simulated by solving three-dimensional elastic wave governing equations with the seismic moment tensor obtained from the Global Centroid Moment Tensor Catalog. Three-dimensional visualization of our computing results displays the nature of the global seismic wave propagation. Comparative analysis of our calculations with observations obtained from the Incorporated Research Institutions for Seismology demonstrates the reliability and feasibility of our numerical results. We compare synthetic seismograms with incorporated and unincorporated ocean models. First results show that the oceans have obvious effects on the characteristics of seismic wave propagation. The peak displacement and peak velocity of P waves become relatively small under the effect of the ocean. However, the effect of the ocean on S-waves is complex. The displacement and velocity of S waves decrease rapidly over time using an unincorporated ocean model. Therefore, the effects of the ocean should be incorporated when undertaking quantitative earthquake hazard assessments on coastal areas. In addition, we undertake comparative analysis on the characteristics of the Earth’s oscillation excited by the 2004 Sumatra-Andaman, 2008 Wenchuan, and 2011 Tohoku earthquakes that incorporate the effect of the Earth’s gravitational potential. A comparison of the amplitude spectra of the numerical records indicates that energy released by the three big earthquakes is different. Our comparative analysis realizes that the computing results can accurately reproduce some eigenfrequencies of the Earth, such as toroidal modes 0T2 to 0T13 and spheroidal modes 0S7 to 0S31. These results demonstrate that numerical simulations can be successfully used to investigate the Earth’s oscillations. We propose that numerical simulations can be used as one of the major tools to further reveal how the Earth’s lateral heterogeneities affect the Earth’s oscillations.