HR: 1330h
AN: S42B-0158    [PDF]
TI: Development of quick and accurate automatic hypocenter location system for the earthquake alarm
AU: Horiuchi, S
EM: horiuchi@bosai.go.jp
AF: National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba, 305-0006 Japan
AU: * Kamimura, A
EM: kamimura@bosai.go.jp
AF: National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba, 305-0006 Japan
AU: Negishi, H
EM: negishi@bosai.go.jp
AF: National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba, 305-0006 Japan
AU: Yamamoto, S
EM: syama@bosai.go.jp
AF: National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennodai, Tsukuba, 305-0006 Japan
AB: Most earthquake damage occurs after arrival of the S wave, whose amplitude is about five times larger than the P wave. Because the P wave travels faster than the S wave, the interval between their arrival times creates an opportunity to activate an earthquake alarm and take preemptive safety measures. We developed an automatic system which transmits the earthquake shaking intensity before S wave arrival. Since the alarm system is used to control transportation, industry, business, etc, at a time of a large earthquake occurrence, false alarms cost huge. We solved the technical difficulty of determining earthquake parameters very quickly and without errors, by developing a novel method using not only P wave arrival times but also time data of P wave not yet arrived. We also developed filters which can distinguish seismic signal from large amplitude noise generated by many kinds of reasons. The system can eliminate extraneous arrival-time readings during the process of hypocenter location by checking automatically measured readings, P wave not yet arrived data, and their station distribution. We use waveform data of Hi-net (High Sensitivity Seismograph Network Japan, National Research Institute for Earth Science and Disaster Prevention) composed of ca. 700 very high quality stations covering whole Japan with space density of 20 to 30 km. All seismometers are installed on observation wells deeper than 100m. Our system can locate precise hypocenters for 97 % felt events occurring in and near Japan Islands within a few seconds and transmits earthquake alarm information before most of seismic energy has arrived even to the station closest to the hypocenter. We are broadcasting earthquake alarm information for all destructive earthquakes by using the satellite system developed by ERI (Earthquake Research Institute, Univ. of Tokyo), and hoping to promote the development of many kinds of automatic control systems which stop cars, factories, etc to protect people from earthquake damage.
DE: 7215 Earthquake parameters
DE: 7223 Seismic hazard assessment and prediction
DE: 7294 Instruments and techniques
SC: Seismology [S]
MN: 2003 Fall Meeting