Application of HVSR technique in the site effects estimation at the south of Marsa Alam city, Egypt

Abstract

The Egyptian government intends to develop the current urban cities especially those located on the Egyptian shorelines, to exploit the ports of these cities to increase the rate of importing and exporting, besides establishing new communities away from the narrow River Nile valley. The southern extension of Marsa Alam city, which is situated on the Red Sea coast will take the chance of development, this city lies south of Hurgada urban city with distance of 310 Km. The area subjects to many earthquakes, particularly from Abu Dabbab active seismic zone.The aim of this paper is using the fundamental frequency term derived from Horizontal to Vertical Spectral Ratio (HVSR) method to evaluate the impact of the surface and subsurface soil sediments on seismic ground motion. Forty-four sites have been chosen for measuring the ambient noise. The obtained zonation map shows that; the lowest value of fundamental frequencies (f0 < 1 Hz) are observed mainly in the regions parallel to the sea coast, these results are compatible with the thickness of sediments in these directions. While the areas aligned at the center of the map are distinguished by a high value of fundamental frequency (f0 = 1–3.7 Hz). On the other hand, the zones extend from the northwest to southeast, west, and south of the study area, characterized by flat HVSR curves. The velocity models derived from seismic refraction and Multi-Channel Analysis of Surface Waves (MASW) approaches show occurrence of shallow bedrock at these zones. The obtained HVSR amplitude (A0) zonation map is compatible with the fundamental frequency (f0) values. Moreover, the fundamental frequency zonation map was simply interpreted taking into account the height of the buildings may be construct in the area. The outcomes will help in understanding the soil-structure resonance phenomena could be happen in the area. The risk of building-soil resonance should be taken in consideration with integration of the provisions of the Egyptian Seismic Code to overcome the probability of buildings collapsing due to the seismic activity in vicinity of the study area.