Estimation of Shear Wave Velocity Profiles Employing Genetic Algorithms and the Diffuse Field Approach on Microtremors Array: Implications on Liquefaction Hazard at Port of Spain, Trinidad

Abstract

This book chapter explains the methodology to determine the shear wave velocity V S profile employing microtremors array data at Port of Spain, Trinidad, and its implication in the seismic amplification and liquefaction hazard in the city. We divide this study into five sections; firstly, we introduce a description of the spectral autocorrelation method and the genetic algorithm schemes to retrieve the Vs and thickness of soil layers. Secondly, we validate the soil profiles via inspection of the ellipticity pattern at such sites; we also compared the observed horizontal-to-vertical spectral ratios (H/V) with the synthetic ones derived by the Diffuse Field Approach and 1D theoretical SH wave amplification functions. Thirdly, we compute the shear wave velocity in the first 30 m obtained from our genetic inversion and compared with the ones estimated by the empirical formulas based on geomorphological conditions. Fourthly, we present a preliminary liquefaction hazard map based on the level of H/V microtremor ratios and the fundamental period of vibration. Finally, we conclude with further recommendations for planning purposes in the city of Port of Spain.