HR: 0830h
AN: S51E-0104    [PDF]
TI: Reduction of Ground Motion Variability Using the Variance Components Technique
AU: * Tsai, C P
EM: ctsai@earth.sinica.edu.tw
AF: Inst. Earth Sciences, Academia Sinica, 128 Academia Rd., Sec. 2, Nankang, Taipei, 115 Taiwan
AU: Chen, Y
EM: yhchen@stat.sinica.edu.tw
AF: Inst. Statistical Science, Academia Sinica, 128 Academia Rd., Sec. 2, Nankang, Taipei, 115 Taiwan
AB: The 1999 Chi-Chi earthquake created a significant increase of strong-motion data set in Taiwan. Data from the main shock and aftershocks of the Chi-Chi event and those occurred elsewhere around this area offer an opportunity to explore the variability of ground motion estimates in Taiwan. Using the variance components technique, Chen and Tsai (2002) decomposed efficiently the prediction errors of ground motions into three components: the earthquake-to-earthquake, the site-to-site, and the residual. From a data set of over thirty thousand records of various site conditions, the percentages of variances of the prediction errors, partitioned into the earthquake and site components, are dependent on the numbers of earthquake events and stations in the sampled records; however, both the variances are in general smaller than that of the residual. It is apparent that the path-to-path component of the variability of ground motions is embedded in the ­residual.­" Empirically based on the estimated variance components, the path component of variance is approximately comparable to those of the earthquake and the site. Thus, the prediction errors of ground motions can be further partitioned into earthquake-to-earthquake, site-to-site, and path-to-path components, and the remaining ­smaller residual.­" From the data in Taiwan, the variability of the site and path components is more coherent in space than that of the earthquake. This implies that the site and path components of variability are more feasible to be extracted from the total prediction errors than the earthquake component. The results show that the prediction errors of ground motions reduce dramatically after ground motion estimates have been corrected for the site-to-site and path-to-path components of variability. This reduction of ground motion variability has significant implications for probabilistic seismic hazard analysis.
DE: 7200 SEISMOLOGY
DE: 7212 Earthquake ground motions and engineering
DE: 7215 Earthquake parameters
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting