Abstract
Western Saudi Arabia is tectonically considered as a region of low seismic activity. However, historical and instrumental records reflect some potentiality of earthquake and volcanic activities for the global importance of Al-Madinah City and surrounding areas, it was important to investigate the current state of ground motion affecting this region in light of the historical eruption of AD 1256 and the seismic swarm of 1999 in Harrat Rahat and the seismic swarm of 2009 in Harrat Ash Shaqa (Lunayyir), which forced the evacuation of more than 40,000 of the inhabitants of Al-Ays Town and its surroundings, some 220 km to the northwest of Al-Madinah City. This study is an attempt to develop peak ground velocity (PGV) and acceleration (PGA) maps for western Arabia using four different empirical ground motion relations. We integrated a large dataset merging the current seismicity that has occurred in the western Arabia with those of historical earthquakes and volcanic activities. This study shows that the maximum PGA and PGV values are found in the Gulf of Aqaba with average values of 310 cm/s(2) and 52 cm/s, respectively. The Red Sea rift zone comes next with average PGA values between 150 and 230 cm/s(2) and PGV values of 24-41 cm/s. Al-Madinah City exhibits an average value of 22 cm/s(2) and 6 cm/s, for PGA and PGV, respectively.