ORIGINAL PAPER Spatial distribution of the empirical peak ground motion in Western Saudi Arabia and its implication on Al-Madinah City Mohamed F. Abdelwahed 1,2 & Nabil N. El-Masry 1,3 & Atef Qaddah 1 & Mohamed R. Moufti 1 & Faisal Alqahtani 1 Received: 12 December 2018 / Accepted: 22 January 2020 # Saudi Society for Geosciences 2020 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. Keywords Ground motion empirical relations . Peak ground acceleration . Al-Madinah seismicity . Historical eruption . Western Saudi Arabia Introduction Al-Madinah City is located at the northern perimeters of the Harrat Rahat monogenetic volcanic field in western Saudi Arabia. Historically, this region experienced many significant earthquake events (Ambraseys and Melville 1988 & Ambraseys and Melville 1989; Ambraseys and Adams 1988; Poirier and Taher 1980). Due to the sparse population, the number of documented ground shacking events is quite small. The tectonic setting around Saudi Arabia suggests that large earthquakes might occur along the Red Sea rift zones, the Arabian Gulf, and the Zagros belt (Adams and Barazangi 1984; Al-Amri 2013; Al-Haddad et al. 1992; El-Isa and Al Shanti 1989; Ghebreab 1998; Khair et al. 2000; Roobol and Stewart 2019; Vita-Finzi 2001). Historical records indicate that a prominent volcanic eruption occurred in AD1256 at some 25 km to the south of Al-Madinah City accompanied by relatively strong earthquakes. The eruption was preceded by 3 days of strong earthquake swarm prior to the eruption and led to the formation of a number of scoria cones and lava field that traveled some 20–30 km northward toward Al-Madinah City (El-Masry et al. 2013; Abu-Shamah and Al-Rahman ibn 1267; Al-Hanafi and Ibn Alaad Din 1600; Al-Matari 1339; Al-Samhudi 1481). Recently in 1999, a moderate seismic swarm (~500 events, M3.0) occurred in Harrat Rahat at about 30 km to the southeast of Al-Madinah City. It is likely that much smaller earthquakes that are below the detection capa- bility of the surface instruments might have also occurred. Abdelwahed et al. (2016) suggested that this swarm might be attributed to the intrusion of small magma bodies at depth. In 2009, a stronger seismic swarm (~30,000 events, M5.8) occurred at about 200 km to the northwest of Al-Madinah City in Harrat Ash Shaqa (Lunayyir) that was interpreted as a failed volcanic eruption (Pallister et al. 2010; Hansen et al. Responsible Editor: Abdullah M. Al-Amri * Mohamed F. Abdelwahed mfibrahim@kau.edu.sa; mfarouk40@yahoo.com 1 Geohazards Research Center, King Abdulaziz University, Jeddah, Saudi Arabia 2 National Research Institute of Astronomy and Geophysics, NRIAG, Ismailia, Egypt 3 Geology Department, Faculty of Science, Suez Canal University, Ismailia 41522, Egypt Arabian Journal of Geosciences (2020) 13:222 https://doi.org/10.1007/s12517-020-5123-4