Presenter: Chi-Hsuan Chung
Date: 2017/05/25
Abstract
Lots of infrastructures are under construction in metropolises in Taiwan in recent years and thus leads to the increasing of population density and urbanization in those area. Taiwan islands is located in plate boundaries in which the high seismicity is caused by active tectonic plates. The Chi-Chi earthquake (Mw 7.6) in 1999 caused a fatality of more than 2000, and the Meinong earthquake (Mw 6.5) in 2016 caused a fatality of 117 in Tainan city as well as damages on hundreds of buildings. The cases imply seismic vulnerability of urban area. During the improvements for seismic hazard analysis and seismic design, consideration of seismic site amplifications in different site conditions is one of important issues.
This study used selected and processed strong motion records observed by the TSMIP network. The site conditions considered as Vs30 (the average S-wave velocity at 30 meters below the surface) used in this study were investigated at most stations (Kuo et al. 2012; Kuo et al. 2016). Since strong motion records and site conditions are both available, we are able to use the data to analyze site amplifications of seismic waves at different periods. The result may be a reference for future modification of seismic design codes to decrease potential seismic hazards and losses. Relationships of site amplification factors and Vs30 are therefore derived for strong motions by regression analysis. Soil nonlinearity (decrease of amplifications) has to be considered at soft soil sites during a strong shaking. We also discuss amplification factors in terms of different intensities if data is available.
Reference
Stewart, J.P., Andrew H. Liu, and Yoojoong Choi (2003). Amplification Factors for Spectral Acceleration in Tectonically Active Regions, Bulletin of the Seismological Society of America
Kuo, C.H., C.T. Chen, C.M. Lin, K.L. Wen, J.Y. Huang, and S.C. Chang (2016). S-wave Velocity Structure and Site Effect Parameters Derived from Microtremor Arrays in The Western Plain of Taiwan, Journal of Asian Earth Sciences Kuo, C.H., K.L. Wen, H.H. Hsieh, C.M. Lin, T.M. Chang, and K.W. Kuo (2012). Site
Classification and Vs30 Estimation of Free-Field TSMIP Stations Using the Logging Data of EGDT, Engineering Geology