Liquefaction Hazard assessment using Horizontal-to-Vertical Spectral Ratio of Microtremor

In this paper, the spectral ratio of mmicrotremor, HSVR, is presented for estimating the liquefaction potential of layered soil in the coastal area of the Persian Gulf, which consists of a hard sandstone layer situated between two saturated sandy layers. The surface layer is thin, with a thickness between 2 and 5 meters. The purpose of this paper is to identify the relation between the liquefaction potential, the natural frequency and the amplification factor values using microtremors. Liquefaction assessment was done at 27 stations using the HVSR approach provided by Nakamura [1]. HVSR analysis was carried out using the Geopsy software. According to the results of the analysis, the predominant frequency values range from about 0.8 Hz to 2.4 Hz and the amplification factor values range from 1.1 to 2.8. Based on these parameters, the vulnerability index Kg is determined, which can be used as a parameter in calculating the liquefaction potential of an area. The results show that the vulnerability index is related to the sedimentary depth as well as the frequency and amplification factor. Furthermore, the calculated results confirm that the southern area of Bushehr City, which is larger than other areas, has a high liquefaction potential. Furthermore, it is possible to determine the limit of Kg to estimate the liquefaction hazard. Comparing the results confirms that in Bushehr, a soil layer is liquefiable if its related Kg value is over 1.7. This value may change with the conditions of the layer and the soil specification.