HR: 1340h
AN: S13C-1447    [Abstracts]
TI: The Development of Real-time Strong-motion Observation on the Earthquake Early Warning in Taiwan
AU: * Hsiao, N
EM: naigi@cwb.gov.tw
AF: Central Weather Bureau, No. 64, Gongyuan Road, Taipei, 10048, Taiwan
AU: Shin, T
EM: shin@scman.cwb.gov.tw
AF: Central Weather Bureau, No. 64, Gongyuan Road, Taipei, 10048, Taiwan
AU: Wu, Y
EM: drymwu@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
AB: For the sake of seismic hazards mitigation, a real-time strong-motion monitoring system was implemented by the Central Weather Bureau (CWB) since 1995. After successive refinements during the past decade, the system has been utilized as the basis for the development of the early warning (EWS) application in Taiwan. In order to shorten the earthquake response time, a virtual sub-network approach is utilized at first. Under the practical experiment since 2001, for monitoring inland or near offshore earthquakes with magnitude greater than 4.5, the response time can be shorten as 18.8+-3.8 sec averagely. Therefore, it can provide early warning before S-wave arrival for metropolitan areas located 60 km away from the epicenter. For the sake of further reducing the area of so-called blind-zone which cannot provide early warning, we also attempted to utilize vertical displacement records of P-wave as a basis to issue warnings. As results, we found that the amplitude 0.1 cm can be used as a criterion to judge if an earthquake above magnitude 6.0 is occurring in Taiwan Island. Furthermore, we also derived a set of frequency-based formulas simultaneously, which can be used to estimate earthquake magnitude rapidly. To combine the research results, and under the framework of real-time strong-motion observational network, we designed an earthquake early warning algorithm which is suitable for Taiwan Island. According to the experiment on 7 magnitude-above-6.0 earthquakes took place after 2002, the averaged response times is within 15 sec. Furthermore, the processing time for inland earthquakes can be shorten beneath 10 sec, and the radius of blind-zone is reduced to 30 km. Since 2003, the CWB has been replacing the existing 16-bit digital accelero- graphs used in its real-time strong-motion monitoring to 24-bit instruments at an annual replacement rate of 5 to 10% of the total. Besides, some high quality borehole seismic stations and a cable-based Ocean Bottom Seismographic (OBS) system are planed to implement on and off north-eastern Taiwan since 2007. We will further develop the EWS in response to these new instruments, as well as to any new research ideas.
DE: 7219 Seismic monitoring and test-ban treaty verification
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: 2007 Fall Meeting