Geophysical site investigation and ground response analysis of Bangkok subsoil due to earthquake

Abstract

The potential damages on building and infrastructure could be affected by long-distance earthquakes since the vibrations can appear ground motion amplification during the wave propagation. Bangkok urban area is located a hundred kilometers away from the potential area of the earthquake epicenter. However, some people in Bangkok could feel the shaking during the earthquake. It indicates that the long-period shaking could happen during the earthquake. In line with this phenomenon, this study aims to interpret the amplification effect and spectral acceleration in the local site of Bangkok due to remoted earthquakes. The microtremor measurement was conducted at four locations in Bangkok to obtain the information of the natural frequency of subsoil and verified with boring log and geological data. The horizontal-to-vertical spectral ratio (HVSR) method was applied to estimate ground thickness and shear wave velocity. The next generation attenuation (NGA) models were implemented to generate ground motion at Three Pagoda Fault as the closest active fault from Bangkok. Equivalent linear one-dimensional seismic ground response analysis was then performed to observe the soil behavior and ground motion parameters on the investigated sites. The results could describe the site effect due to earthquake on Bangkok subsoils. In addition, this research assesses spectral acceleration result compared to spectral acceleration design for Bangkok from seismic resistant design of buildings and structures of Thailand. In general, the results are also addressed to make awareness of the earthquakes for the local people.