HR: 16:30h
AN: S44B-02    [Abstracts]
TI: Earthquake Early Warning System in Japan
AU: * Kiyomoto, M
EM: mkiyomoto@met.kishou.go.jp
AU: Tsukada, S
EM: tsukada@met.kishou.go.jp
AU: Ohtake, K
EM: ohtake@eqvol.kishou.go.jp
AU: Shiozu, Y
EM: shiozu@eqvol.kishou.go.jp
AU: Morimoto, M
EM: morimoto.masahiko@met.kishou.go.jp
AU: Saito, M
EM: msaito@met.kishou.go.jp
AU: Sekita, Y
EM: sekita@met.kishou.go.jp
AU: Doi, K
EM: keijidoi@eri.u-tokyo.ac.jp
AU: Yoshida, Y
EM: yyoshida@mri-jma.go.jp
AU: Odaka, T
EM: todaka@rtri.or.jp
AU: Ashiya, K
EM: ashiya@rtri.or.jp
AU: Horiuchi, S
EM: horiuchi@bosai.go.jp
AB: Japan is located in one of the most tectonically active region in the world. We have suffered from many disasters brought by earthquakes and tsunamis. Significant efforts to mitigate disasters have been made as one of the most important national programs. Considering the difficulty of the earthquake prediction in time, Japan Meteorological Agency (JMA) considers it is important to issue the early warning immediately when the large earthquake occurs. JMA has been developing the "Earthquake Early Warning(EEW)" as a countermeasure to strong motion. JMA's EEW estimates hypocenter and magnitude using initial seismic waveform observed at the stations close to the epicenter, and issues estimated seismic intensity before the strong motion arrival. It also enables prompter issuance of the tsunami warning. We adopt a step-by-step method to improve the accuracy and reliance of the estimated focal parameters as the available data increases as the time lapse, ensuring the promptness of the first estimation at the same time. We estimate the hypocenter using Single Station Method and Network Method. Single Station Method is fitting simple function (Bt*exp(-At)) to the absolute value of acceleration waveform envelope of the first two seconds from the P onset by the cooperative study with Railway Technical Research Institute(RTRI). Network Method is using "territory" and "grid search" in combination. In addition to this procedure, we use the result of "Not Yet Arrived Data Method", a kind of grid search method, from June 2005. This method is developed by National Research Institute for Earth Science and Disaster Prevention(NIED). After the hypocenter is determined, we estimate the magnitude by using hypocentral distance and maximum displacement amplitudes (Dmax) updated every second and the formula is as follows: M = log (Dmax) + logR + a1*R + a2 (R: Hypocentral distance (km)) We can calculate each site of Seismic Intensity estimation by using up-to-date hypocenter and magnitude in addition. JMA has started test distribution of EEW in Feb. 2004 to specific users to fieldtest the effectiveness of the warning, for the events that occur in the region where JMA has integrated data processing functions at the seismic stations. EEW issued 245 times from Feb. 25th 2004 to Aug 31st 2005 (including 22 times of false alarm almost due to initial artificial mistakes). We will discuss the detail of EEW distribution at the session.
DE: 0520 Data analysis: algorithms and implementation
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7290 Computational seismology
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: Fall Meeting 2005