A Study on the Classification of Site Effects and Its Correction in Attenuation Relationship of Peak Ground Velocity

• Main Authors: Shun-chiang Chang, 章順強
• Other Authors: Kuo-liang Wen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/2634t7

碩士 === 國立中央大學 === 地球物理研究所 === 97 === The prevention of the earthquake disaster, its primary step lies in the assessment of the earthquake calamity. Earthquake disaster forecast of the traditional manner use to do most of the application of attenuation models. 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. However, Local site characteristics on the value of the largest earthquake has considerable influence, the decay mode set up stations must be taken into account characteristics of the site in order to enhance the reliability of assessment. So, it is necessary to consider the site effects in attenuation relationship of PGV, and the result of predicted in seismic hazard will make best. Generally, site effect is one of the important factors for predicting ground motion. Therefore, the purpose of this study will use seismic records and PGV attenuation relationships between the errors, set up the Site corrections of the attenuation relationships in Taiwan region. First step, we got the first PGA of each site by attenuation relationship of PGV following Chien(2001), which used more than 3000 seismic records from 59 earthquake events to study the attenuation relationship of PGV. Second step, the TSMIP and TREIRS site correction C0 and C1, can be simplified by fallowing the law : ln(PGVObs)=C0+C1×ln(PGVpre), where PGVObs is the observed PGV value, PGVpre is the predicted PGV value obtained by the attenuation relationship laws. The selection criteria are ML > 4.5 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 data from 80 telemetered strong-motion stations to estimated the peak ground motions PDTS at TSMIP sites: PDTS= fTS(f(ML,R),C0,C1)× fRTD(R,D0,D1), where PDTS is the predicted PGV 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 and 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 PGV 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 PGV maps will be useful in earthquake emergency response operations.