UPDATING FRAMEWORK FOR SITE-SPECIFICATTENUATION RELATION OF SEISMICGROUND MOTION IN THAILAND

摘要

We propose the attenuation relations for peak ground acceleration (PGA) and 5% damped spectralacceleration (Sa) applicable to the CMMT site which is located on rock. The CMMT site is located inChiang Mai, the northern part of Thailand. Thailand has only a few ground motion data and most ofpeak ground acceleration are smaller than 1 gal. To overcome this difficulty, a Bayesian updatetechnique was used to construct the attenuation relations for Thailand based on a past attenuationrelation proposed by Idriss (1993). In this study, we added a correction term (site effect term) anderror term to the Idriss attenuation relation using the Bayesian update technique. From the comparisonof the prediction by the Idriss attenuation relation and the observed data, we found that the Idrissattenuation relation overestimates PGA but underestimates Sa. The prediction from the updatedattenuation relation for PGA and Sa proposed by this study is much closer to the observations thanthose by the Idriss attenuation relation.