dc.description.abstract | 158
As a result, we can better understand the attenuation characteristics in Taiwan and
can reliably predict the peak amplitude for strong ground motion when an earthquake
occurs. One of the main factors that affect the attenuation relationship is the existence of
site effects. It is believed that the systematic bias mainly comes form the site effects. So,
it is necessary to consider the site effects in attenuation relationship of PGA, and the
result of predicted in seismic hazard will make best. Generally, site effect is one of the
important factors for predicting ground motion. The TSMIP sites still do not be good
classified. So, in this paper, we used two step to predicted the best result in seismic
hazard. The purpose of this paper is to investigate the classification criterion of local
site effect and its influence in the seismic hazard.
First step, we got the first PGA of site by attenuation relationship of PGA from
Chien(2001), which used more than 3000 seismic records from 59 earthquake events are
used to study the attenuation relationship of PGA. The selection criteria are ML > 5.0
and focal depth < 35 km. All events are well recorded by the TREIRS system and
TSMIP system. These events occurred in 1995 to 1999, are widely felt in Taiwan. These
earthquakes are relocated by this study by using both the TREIRS with TSMIP systems
records. The standard deviation of the residuals between the observed and predicted
values (i.e. ln(observed)-ln(att. form) ) are 0.7654.
Second step, the TSMIP and TREIRS site correction C0、C1, can be simplified by
fallowing the law : ln(PGAobs) S=C0+C1*ln(Yatt)S, where (PGAobs) S is the observed
PGA value, (Yatt)S is the predicted PGA value obtained by the attenuation relationship
laws calacted. The selection criteria are ML > 4.0 and focal depth < 35 km. All data of
site are well recorded by the TREIRS system and TSMIP system. The results agree
reasonably well with the surface geology from published maps.
Generally, the attenuation relationship and site corrections represent a statistically
average effect. But, every event possesses its own characteristics, such as the source.
Therefore, we used TREIRS system datas from 75 telemetered strong-motion stations to
estimated the peak ground motions PDS at TSMIP
sites: ) , , ( 1 0 D D R f y PD S s S S
× = ,where S S y is the predicted PGA value obtained by
the attenuation relationship, R is the ratio by observed value at the TREIRS system
station and the predicted value by the attenuation relationship with site correction at the
TREIRS system station, D0、D1 are coefficient to correct the amplification by TSMIP
system station.
With the attenuation relationship and the site corrections data base, we have
embarked on a practical but yet important problem of predicting the PGA values as soon
as a large earthquake happens in Taiwan. The only input this extreme values prediction
calculation system needs is the TREIRS system solution. We expect that the predicted
PGA maps will be useful in earthquake emergency response operations. | en_US |