Seismic Hazard Assessment for Sohar Region, Northern Oman

Probabilistic seismic hazard assessment (PSHA) was conducted at the ground surface of few important areas of Sohar region, including a site-specific response analysis. The assessment starts with compiling a comprehensive and homogeneous earthquake catalogue. This catalogue was declustered to include only independent events and then tested for the completeness of different magnitude ranges. Two alternative seismotectonic models for the region were identified and their earthquake recurrence parameters were estimated using the doubly bounded exponential distribution. Ground-motion prediction equations (GMPEs) were selected from validated models for the Middle East region. These GMPEs were used to calculate the seismic hazard levels in terms of hazard curves and 5% damped Uniform Hazard Spectra (UHS) for 475, and 2475 years return periods, including Peak Ground Accelerations (PGA) and Pseudo-Spectral Accelerations (PSA) for important response periods for engineers. The performed site characterization study of the areas provides the fundamental frequency, Vs30, amplification spectra, and the ground surface seismic hazard maps.

The ground surface seismic hazard maps were provided, with return periods of 475 and 2475 years. The PGA values at the area ranges between 79 to 194 cm/sec2 for 475 years return period and between 179 to 429 cm/sec2 for 2475 years return period. The seismic hazard at the surface level in terms of 5% damped Uniform Hazard Spectra (UHS) for 10% and 2% probability is provided. The maximum spectral ground accelerations reach 210 and 1264 cm/sec2 for spectral period 0.2 sec for return periods of 475 and 2475 years, respectively. Spectral accelerations at short and 1.0 sec response periods correspond to the SS and S1 parameters that were defined according to the (ASCE 7-10) are estimated and adjusted to derive the corresponding design spectral ground-motion (SDS and SD1).