S. I. GSF 2018 Deaggregation of probabilistic seismic hazard for selected cities in the Arabian Peninsula Yousuf Al-Shijbi 1 & Ahmed Deif 1 & Issa El-Hussain 1 & Adel M. E. Mohamed 1,2 & Amna Al-Dairi 1 Received: 21 January 2019 /Accepted: 31 July 2019 # Saudi Society for Geosciences 2019 Abstract Probabilistic seismic hazard assessment (PSHA) for 26 cities in the Arabian Peninsula in terms of unified hazard spectra at rock conditions for 475 and 2475 years return periods was performed. PSHA integrates overall potential earthquake sources with various magnitudes and distances with resulting ground motion prediction intensities. The combination of all these scenarios together cannot inform which particular scenario is most likely contributing to the rate of exceedance of a given ground motion intensity. In order to determine which earthquake contributes most to the hazard, PSHA results are deaggregated for the selected cities based on equal spacing in magnitude and distance for the amplitudes of PGA, SA (T = 0.2 s), SA (T = 1.0 s) and SA (T = 2.0 s) at 2% and 10% probability of exceedance in 50 years (equivalent to 2475, and 475 year return periods, respectively). Seismic hazard at cities close to major active tectonic structures is influenced mostly by earthquakes at nearby distances for both 475 and 2475 years return periods for all considered spectral periods. For cities close to low active seismic sources or relatively far away from the major tectonic elements, the seismic hazard is generally controlled by remote larger earthquakes for long spectral periods and by nearby small to moderate events for shorter ones. Keywords Seismic hazard . Deaggregation . Arabian peninsula Introduction Factors such as earthquake magnitude, epicentral distance, duration, soil condition, topography, damagability/ vulnerability characteristics of the built environment as well as of the society influence the degree of damage and casualty caused by earthquakes. Moreover, small- and medium-size earthquakes could have a high impact on the intensity of dam- age to structures that do not meet the seismic codes regula- tions. In order to decrease the seismic risk, the best method is to accurately design and build earthquake-resistant structures. When calculating seismic hazard using the PSHA approach, all possible earthquake scenarios (magnitudes and distances) are used as inputs. Uncertainties in seismic source models, earthquake magnitude, earthquake location, recurrence inter- vals, and ground motion prediction equations (GMPEs) are also included. The most common outcome of PSHA is the hazard curve (HC), which is a plot showing the change in ground motion amplitude relative to the annual frequency of exceedance (reciprocal of return period). Another common re- sult of PSHA is the Uniform Hazard Spectrum (UHS), which is the most widely used representation of seismic actions in the earthquake-resistant design. UHS curves illustrate ground mo- tion amplitudes over a number of spectral periods of engineer- ing interest using response spectral ground motion prediction relationships at a specific return period. The HC as the main result of performing PSHA illustrates the accumulating effect of all possible earthquake scenarios on the probability of exceeding a given ground motion level. Therefore, it is not immediately obvious to understand from the HC which scenario is most likely controls the hazard at a given ground motion level and the design earthquake definition at a site is out of reach (McGuire 1995). In order to define which earthquake dominates the hazard at the site, the HC is broken down into its contributions by magnitude and distance through a process known as seismic hazard deaggregation (McGuire 1995; Bazzurro and Cornell 1999). Deaggregation helps to fill This article is part of the Topical Collection on Seismic and Earthquake Engineering Studies in the Arabian Plate and the Surrounding Region * Yousuf Al-Shijbi alshijbi@squ.edu.om 1 Earthquake Monitoring Center, Sultan Qaboos University, Muscat, Oman 2 National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt Arabian Journal of Geosciences (2019) 12:518 https://doi.org/10.1007/s12517-019-4704-6