Probabilistic Seismic Hazard Deaggregation for Selected Egyptian Cities

Abstract

A probabilistic seismic hazard analysis in terms of peak ground acceleration (PGA) and spectral acceleration (SA) values has been performed for the Egyptian territory. Eighty-eight potential seismic sources (for shallow- and intermediate-depth seismicity) in and around Egypt were identified and characterized based on an updated and unified earthquake catalog spanning the time period from 2200 B.C. until 2013 A.D. A logic-tree approach was followed, after a sensitivity analysis, to consider the epistemic uncertainty in the different input parameters, including the selected ground-motion attenuation models to predict the ground motion for the different tectonic environments. Then the seismic hazard deaggregation results, in terms of distance and magnitude, for the most important cities in Egypt have been computed to help understanding the relative contributions of the different seismic sources. Seismic hazard deaggregation, in particular, was computed for PGA and SA at periods of 0.2, 1.0 and 2.0 s for rock-site conditions, and for 10% probability of exceedance in 50 years. In general, the results at most of the cities indicate that the distance to the seismic sources which mostly contribute to the seismic hazard is mainly controlled by the nearby seismic sources (especially for PGA). However, distant events contribute more to the hazard for larger spectral periods (for 1.0 and 2.0 s). A significant result of this type of work is that seismic hazard deaggregation provides useful data on the distance and magnitude of the contributing seismic sources to the hazard in a certain place, which can be applied to generate scenario earthquakes and select acceleration records for seismic design.