A Study on the Site Effects of Attenuation Relationship of Peak Ground Acceleration Correction
Hao-Kai Chan
Abstract
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 < 50 km. All events are well recorded by the TREIRS system and TSMIP system. These events occurred in 1995 to 2007, are widely felt in Taiwan. These earthquakes are relocated by this study by using both the TREIRS with TSMIP systems records.
Second step, the TSMIP and TREIRS site correction C0ĦBC1, 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 < 50 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.
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.