Efficiency of horizontal-to-vertical spectral ratio (HVSR) in defining the fundamental frequency in Muscat Region, Sultanate of Oman: a comparative study

Abstract

Muscat region is the most important political, economic, and densely populated region in the Sultanate of Oman. The proximity of Muscat region to the Oman Mountains and Makran subduction zones controls the earthquake hazard for Muscat. Evidences indicate the occurrence of a nearby historical earthquake with moderate magnitude M S = 5.5 in 1883. This event led to the damage of some villages near Nizwa City. The main objective of the current study is to compare the site characteristics of the region of interest in terms of the fundamental frequency using microtremors measurements with the numerical analysis results using one-dimensional (1-D) shear wave profiles. The microtremor measurements were performed at 99 sites distributed over the study region in order to calculate the horizontal-to-vertical spectral ratio (HVSR). The numerical modeling of horizontal shear (SH) waves in soil at the selected 99 sites are assessed by carrying out 1-D ground response analysis using the program SHAKE91. The required shear wave velocity profiles for the numerical modeling of SH-waves were derived using multichannel analysis of surface waves profiles. The amplification spectra have been evaluated for the soil column at each site location and the fundamental frequency obtained using SHAKE91 and HVSR are compared. Results were found to be compatible with the general surface geology of the region of interest and in most cases the HVSR is proved to be suitable for calculating the fundamental frequency in Muscat region.