Estimating the near-surface site response to mitigate earthquake disasters at the October 6th city, Egypt, using HVSR and seismic techniques

Abstract

The damage caused by earthquake occurrences in different localities necessitates the evaluation of the subsurface structure. A priori estimation of the site effects became a major challenge for an efficient mitigation of the seismic risk. In the case of moderate to large earthquakes, at some distances from large events, severe damage often occurred at zones of unfavorable geotechnical conditions that give rise to significant site effects. The damage distribution in the near-source area is also significantly affected by fault geometry and rupture history. The microtremor (background noises) and shallow seismic surveys (through both the seismic refraction and Multi-channel Analysis of Surface Waves (MASW)) were carried out in a specific area (The club of October 6 city and its adjacent space area). The natural periods derived from the HVSR (Horizontal to Vertical Spectral Ratio) analysis vary from 0.37 to 0.56s. The shallow seismic refraction data, which were conducted at the area, are used to determine the attenuation of P-waves (Qp) in different layers, using the pulse-width technique. The evaluation of the site response at the studied area yields amplification factor of the ground motion, ranging between 2.4 and 4.4.