Local Site Effects on Seismic Ground Response of Dubai-Sharjah Metropolitan Area

Abstract

This paper investigated the influence of local geotechnical and geological soil conditions on the intensity of ground shaking of Dubai-Sharjah metropolitan area (DSMA). Acceleration-time histories of Dubai and Sharjah were chosen according to spectral shape and similarity in magnitude and distance to a target response spectrum that were obtained from the results of Seismic Hazard Analysis (SHA). Subsurface geotechnical data of 72 different sites, located in the area under consideration, were used in this study. The effect of local site conditions on ground response during earthquake has been evaluated by performing equivalent linear analysis. Dynamic properties of selected soil profiles were evaluated using empirical relations between Standard Penetration Test (STP) N-values and shear wave velocity (Vs). Modulus degradation and damping curves for sand and rock were also employed in the analysis. Results indicated that surficial deposits in the area amplified earthquake ground motion. The peak amplification was observed over relatively narrow frequency range of 1.5-5 Hz (0.2-0.8s period) that was found to represent the predominant frequency range of the site classes under consideration. Amplification factors at PGA and at both short and long periods (0.2s and 1.0s), which are site class dependent, were compared to the current code of practice.