Toward rapid and precise source analysis using teleseismic body waves and tsunami waves: In case of the 2010 Chile earthquake

Abstract:

To provide accurate forecasts of arrival times and waveforms of tsunamis caused by great earthquakes, it is important to rapidly and precisely determine a source using real-time tsunami waveforms and teleseismic body waves data. In order to do that, the Green's function and the "tsunami" Green's functions that can be calculated with a low computational cost and predict observed waveforms precisely are required. We separately inverted the 2010 Chile earthquake using teleseismic body waves and tsunami wave. The Green's functions of teleseismic body waves inversion and the "tsunami" Green's functions of tsunami waveforms inversion are used a full-waveforms calculated by the Direct Solution Method [e.g., Kawai et al. 2006] and a phase-corrected long-wave proposed by Watada et al. [2014], respectively. The phase corrected tsunami Green's functions include the effects of the long wave dispersion caused by the elasticity of the sea bottom, compression and dilatation of sea water, and gravitational potential change associated with mass motion during tsunami propagation of sea water. The slip distributions obtained by the teleseismic body waves and the tsunami waveforms data are almost consistent. The synthetic seismograms are explained the observed waveforms well including later arriving PP waves and W phase, which cannot calculate the conventional ray theoretical Green's functions. The synthetic tsunami waveforms also well explained the observed waveforms near and far-field DART data. The tsunami waveforms inversion without phase corrections cause an apparent shift of the large slip area away from the stations i.e., toward deeper part of the fault, because of faster propagation speed of conventional linear long wave tsunami Green's functions. Furthermore, the teleseismic body wave inversion obtained by conventional ray theoretical Green's functions also cause a wrong results. The main reason is that the ray theoretical Green's functions cannot calculate the W phase. A database of full-waveforms Green's functions (e.g., Pre-calculated Pyrocko GF Stores) make it possible to analyze rapidly and routinely source processes of great earthquakes. The new phase-corrected tsunami Green's functions is also able to calculate not much time than the conventional linear long wave tsunami Green's functions.