2019 Volume 19 Issue 6 Pages 6_105-6_115
An on-site earthquake warning for the threshold of earthquake motion is generally applied to an amplitude of S-wave, which is dominated in seismic waves. To issue the earthquake warning for the threshold of earthquake motion earlier, in this study, we investigated the applicability of earthquake warning for the threshold of P-wave in seismic data, using an amplitude ratio of S-wave to P-wave. At first, we theoretically led that the amplitude ratio of S-wave to P-wave were affected by both subsurface P-wave and S-wave velocity structures at the site. Also, we could stably extract the amplitude ratio of S-wave to P-wave, using seismic data recorded. As the results, S-waves predicted by P-waves using the amplitude ratio of S-wave to P-wave at seismic stations were in good agreements with observations. Finally, we concluded that this method can potentially issue the earthquake warning earlier than the previous method by the time of Ts-p.
