Seismic Hazard Assessment of Al Mashair Area, Makkah Al-Mukaramah (Saudi Arabia)

Makkah is one of the most important cities not only in Saudi Arabia but also for all Muslims all over the world. Recently, it has experienced strong earthquakes that caused panic due to the fact that it is mostly occupied by soft Quaternary deposits overlying basement rocks. The spatial variation of ground motion in Al Mashair area was estimated by generating synthetic ground motion considering the point source model coupled with site response analysis. The rock level peak ground acceleration time histories was simulated at 87 sites in Al Mashair area for maximum credible earthquake moment magnitude 5.0. The results are presented in the form of peak ground acceleration (PGA) at rock level. In addition, the ground surface acceleration assessed by horizontal to vertical spectral ratio technique based on microtremor measurements at 87 sites. The ground surface response spectral curves with 5% critical damping were calculated using shear wave velocity calculations from the MASW results and the earthquake time histories. Surface response spectral values were mapped using the GIS platform at 1.5, 3.0, 5.0, 8 and 10 Hz. The surface ground motion maps show that the hazard level ranges from low to moderate with spectral acceleration (SA) in the range from 13 to 124 cm/s².