dc.description.abstract | Based on the real-time strong-motion monitoring system implemented by
Central Weather Bureau (CWB), we developed and evaluated the earthquake
early warning (EEW) application in Taiwan. In the study, we mainly
concentrated our attention upon two essential parts of EEW, which one is rapid
determination of earthquake parameters, and the other is accurate prediction of
peak ground motions.
On determining earthquake parameters, 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.
As regards the prediction of peak ground motions, we use two-step linear
regression analysis to derive various parametric equations. The parameters
include peak ground acceleration (PGA), peak ground velocity (PGV), 0.3 sec,
1.0 sec, 3.0 sec spectral acceleration (Sa) and filtered PGA etc.. According to
the earthquake early warning and rapid reporting stages respectively, we
developed three algorithms creating “ShakeMaps” based on these predictive
equations. In comparison with actual maps resulted from observed
strong-motion data, the predictive results had high similarity, the correlation
coefficients are almost above 0.8 and the average magnifications of grids are
between 0.5 to 1.5.
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. Except for the Chengkung earthquake of 2003,
the processing time for inland earthquakes can be shorten beneath 10 sec
further, and the radius of blind-zone is reduced to 30 km. | en_US |