EFFECT ON UNCERTAINTY OF BEDROCK TYPE & ITS LOCATION ON SEISMIC SITE CHARACTERIZATION

Abstract

It has been recognized that soil conditions and geological conditions at local sites significantly influence the strong ground motions. The accurate estimation of site amplification is required for seismic hazard prediction at any site. For strong ground motion the most important parameter that effect the local site condition is the location of bedrock and its type. The variation in bedrock depth modifies the dynamic of system and also influences the bedrock motion amplification. Due to impedance contrast between soil layer and bedrock, surface amplification is influenced. Seismic response is influenced by the location of bedrock and type of bedrock too. In this dissertation work an attempt has been made to investigate the effect of bedrock type as well as bedrock location through one dimensional equivalent linear ground response analysis. Different types of bedrock at different locations have been considered for the analysis. SHAKE2000 software has been used for one dimensional equivalent linear ground response analysis. Three earthquakes have been considered to simulate near field effects. Results has been elucidated in terms of response spectra for 5, 10 and 15% damping, acceleration time history for surface, amplification factor and Fourier spectrum. It was concluded that bedrock motion amplification is inversely related to bedrock depth i.e., as the depth of bedrock location increases amplification decreases. It was also concluded that peak ground acceleration also increases while increasing the bedrock shear velocity.