Earth Planets Space, Vol. 60 (No. 10), pp. 1053-1057, 2008LETTER
Changjiang Wu and Shigeki Horiuchi
National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba, Ibaraki 305-0006, Japan
(Received June 29, 2007; Revised November 21, 2007; Accepted December 5, 2007; Online published November 7, 2008)
Large earthquakes have been observed to be caused by the rupture of several asperities. The rapid determination of source parameters is hence of great importance for correctly determining shaking intensities or evaluating the strong motion distribution generated by a large earthquake. This study shows that we can automatically preprocess strong motion data using automatic P- and S-phase pickers, determine the focal mechanism, and identify the fault plane from two nodal planes. A real-time simulation is performed for the 2007 Noto Hanto earthquake. Using our automatic fault plane identificator, we were able to identify one of the nodal planes with a strike of 62° and a dip of 70° within a 30-s interval from the beginning of focal mechanism determination to the end of waveform inversion. Results from automatic inversions showed that the slip was confined to a shallow portion with a maximum slip of about 3 m. The total seismic moment released in 10 s was 2.0 × 1018 N m, which corresponds to a moment magnitude of 6.8.
Key words: Real-time, earthquake, source parameter, rupture process.