HR: 0800h
AN: S51D-1030    [Abstracts]
TI: A single station approach for earthquake early warning in Taiwan
AU: Yen, H
EM: r93224204@ntu.edu.tw
AF: National Taiwan University, Department of Geosciences, No. 1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AU: * Wu, Y
EM: drymwu@ntu.edu.tw
AF: National Taiwan University, Department of Geosciences, No. 1, Sec. 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Liang, W
EM: wtl@earth.sinica.edu.tw
AF: Academia Sinica, Taiwan, Inst. Earth Sciences 128 Academia Road, Sec. 2, Nankang , Taipei, 115 Taiwan
AB: Most earthquake hazards are usually from strong shaking caused by S and surface waves. The P wave propagates faster than S wave, moreover, the P wave carries information and S wave carries energy. Thus, analyzing the P wave information to obtain earthquake parameters, it can issue warning for some areas to mitigate the damage before the S wave arrival. Two approaches of earthquake early warning system (EWS) have been tested: (a) Regional warning, and (b) Onsite warning. In (a), the traditional seismological method is used to locate an earthquake, determine the magnitude, and estimate the ground motion in the region involved. In (b), the beginning of the ground motion (mainly P wave) observed at a site is used to predict the ensuing ground motion (mainly by S and surface waves) at the same site; usually no attempt is made to locate the event and estimate the magnitude. In the past, the researches on EWS in Taiwan mainly use regional warning approach. Few efforts pay on the onsite warning, which might provide more rapid information. Therefore, in this study we investigated a single station approach for onsite EWS. We selected waveform data from the NACB station of the BATS with magnitude large than 4.0 and focal depth less than 30 km from 1996 to 2002 for this purpose. The average period computed for the initial 3 sec of P wave (Kanamori, 2005) showed a logarithm linear relation with magnitude, implying that the earthquake magnitude can be determined from averge period with a standard deviation of 0.6. We further calculated the peak displacement amplitude from the initial 3 sec of P wave (Pd, Wu and Kanamori, 2005). It correlates well with the peak ground-motion velocity (PGV) at the NACB station. Therefore, by using Pd, we may predict the shaking intensity for earthquake early warning purposes. We also try to determine the epicenter using initial 3 sec of P wave. Based on the Pd attenuation relationship between Pd and magnitude, the hypocentral distance could be estimated. The ratio of the calculated-to-observed hypocentral distance varies from 0.41 to 1.71 with minus/plus one standard deviation range. Back azimuth could be estimated from particle motion from initial 3 sec of P wave with a standard deviation of 40 degrees. It is workable to conduct the EWS based on our results for single station approach.
DE: 7200 SEISMOLOGY
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7215 Earthquake source observations (1240)
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: Fall Meeting 2005