Abstract:
In the past, there was no attenuation relationship specifically developed for Thailand to be used in probabilistic seismic hazard analysis when the seismic hazard map was prepared for Thai seismic design code. It was primarily due to the lack of strong ground motion records, e.g., magnitude (Mw) larger than 4.5 and site-to-source distance less than 200 km, in Thailand. Therefore, existing attenuation models developed from data in other regions had to be adopted. However, there was an earthquake with Mw=6.8 occurred in Myanmar on March 24, 2011 and its epicenter was located only 30 km away from Mae Sai district in Chiang Rai province, Thailand. The seismic recording stations of Thai Meteorological Department (TMD) were able to record a strong ground motion at Mae Sai and several moderate ground motions at many stations through-out the country. These new data provide an opportunity to study and review the attenuation model that is appropriate for Thailand region. This research thus aims to collect all available recorded ground motions in the Thailand up to present, and use them to develop attenuation equations to estimate ground motions, e.g., peak ground acceleration and spectral acceleration, in Thailand region. The data are classified as being recorded on rock or soil site, and categorized according to the corresponding Plate tectonics. The spectral acceleration was calculated for natural period for 0.2 and 1 seconds The results are expected to provide more reliable estimation of ground motion intensity for Thailand region.