Abstract
Site response characteristics have a significant influence on ground motion vibrations. To evaluate the site response effects at King Saud University campus, the horizontal-to-vertical spectral ratio (HVSR) technique has been applied at 45 sites with about 400-m spacing. The recording time was more than 1 h at each site with a sampling rate of 100 Hz. The data were processed and analyzed using Geopsy software to produce measurements of fundamental frequency and minimum site amplification factor. Moreover, shear-wave velocity down to 30-m depth has been acquired at 10 measuring sites in the campus. In addition, geotechnical borehole data were collected from four boreholes within the campus. Generally, in majority of sites the H/V curve for amplitude spectra displayed a clear peak, signifying the presence of a sharp soil-bedrock impedance contrast between alluvial deposits and underlying bedrock. It is indicated that the fundamental frequency ranges between 0.64 and 1.94 Hz. Given the measured resonance frequency of around 1 Hz, buildings located on the alluvium that have 5 stories in height could experience soil-structure resonance, while the amplification factor varies from 1.19 to 11.22 indicating localized zones having high vulnerability index due to the considerable thickness of alluvial deposits. Moreover, shear-wave velocity ranges between 320 m/s and 684 m/s revealing zones of stiff soil to very dense soil/or soft rock which is correlated well with the geotechnical parameters of borehole data. Based on these results, the ground conditions of near-surface sediments in the King Saud University campus indicate weak zones that led to ground subsidence resulting in differential settlements of foundations.