Seismic Site Effects of Soil Amplifications in Bangkok

Abstract

In this paper, seismic site effects resulting from amplification of soft soil in Bangkok are presented.  Site characteristics were surveyed using the microtremor observation technique.  The method of Centerless Circular Array (CCA) was employed to examine the shear wave velocity profile of subsoil from surface to bedrock level of 20 sites.  The average shear wave velocity of each site is not significantly different; however, the depth of bedrock varies from 400 to 800 m. The area was subdivided into two zones according to the depth of bedrock.  The results of shear wave velocity were then used to construct a model for ground response analysis for prediction of earthquake motion at the surface.    The design response spectral accelerations were presented for the two zones.  The results show that higher ground accelerations could occur in the area having shallow depth of bedrock, less than 700 m.  The design response spectral accelerations are generally high in the periods range from 0.5 to 4 second.