We present a probabilistic seismic-hazard analysis (PSHA) for the west-central part of the Arabian Peninsula. Our study area includes the northern Harrat Rahat volcanic field and the nearby city of Al Madīnah, Kingdom of Saudi Arabia. This young, active volcanic field experienced one historical eruption in 1256 C.E. (654 in the year of the Hijra) that vented 20 to 22 kilometers (km) southeast of the center of Al Madīnah, which has a present population of about 1.4 million. The field also erupted numerous times in the late Pleistocene and possibly in the early Holocene. We used recently developed regional ground-motion prediction equations for Saudi Arabia to calculate the severity of ground shaking as a function of distance from the earthquake source. This information was combined with two key volcanic parameters for this area: (1) the return period of volcanic eruptions and (2) the spatial probability of the next vent opening. The calculated ground-motion levels of peak ground acceleration and peak ground velocity with a 2-percent probability of exceedance in 50 years are expected to be about 0.14 the acceleration due to gravity (g) and 10 centimeters per second (cm/s), respectively, at the most probable vent opening location, about 25 km southeast of Al Madīnah’s center, and about 0.07 g and 3 cm/s, respectively, in the city interior. These ground motions are higher than previous estimates that did not consider the nearby earthquakes associated with volcanic activity.
