Local Site effects for ground motion acceleration and amplification at Bahrah, Saudi Arabia.

Abstract

The soil conditions variability at site strongly influence ground motions during earthquakes. The disastrous earthquakes have shown that the local site conditions are the essential factors that impact lsurficial ground motions. In present study, local site effects are evaluated for ground motion acceleration and amplification at Bahrah. The town is situated on which is covered by quaternary alluvial wadi deposits. The ground motion time series are obtained through Spectral matching technique. is utilized to generate well matched ground motion time series based on the results of the PSHA and the deaggregation process. The ground motion time series and shallow Geophysical data are utilized to carry out One-dimensional simulation is carried out for equivalent linear seismic response analyses for soil layers. Results of One-dimensional site response analysis are interpolated to generate maps that account for ground motion accelerations and amplifications at top of the soil for selected spectral periods (PGA, 0.1, 0.2 and 2) for 475 years return period. The maps show the ground shaking rather than the probability of damage to buildings. The maximum values of amplification ranges upto 3.46 and acceleration upto 0.86 g. The undulation of bed rock topography and existence of deep soft sediments are reflected considerably on the results of the study area. The surface ground motion maps show that the seismic hazard level in Bahrah is moderate.