الملخص الإنجليزي
The seismotectonic setting around the Arabian Plate strongly suggests that medium to large earthquakes are possible, particularly along the edge of the plate. The seismic hazard for the Arabian Plate is calculated utilizing the probabilistic approach within a logic-tree framework. Earthquake catalogue for the Arabian Plate has been compiled using the databases from new and revised international, regional, domestic catalogues and several research publications include all events having an assigned magnitude 4.0 or above on any magnitude scale. The area of investigation was subdivided into four polygons, within each polygon a priority was given in selecting earthquake record. A total of 11402 instrumental earthquakes for the period of 1900 – 2010 were merged with about 509 historical events reported during 19 AD to 1899. The catalogue is magnitude homogenized by converting the different scales into moment magnitude (Mw) using the orthogonal regression that considers random errors in both the independent and dependent variables. The catalogue is then declustered in order to identify and eliminate the dependent events. This step was followed by testing the catalogue for the completeness at different magnitude ranges. The declustered earthquake catalogue derived for the Arabian Plate contains 5528 main shocks and is used to evaluate the earthquake potential in each seismic source zone.
A seismotectonic source model was constructed taking into consideration all the seismic sources that might affect the Arabian plate. A total of 65 seismic source zones including background ones are used to define the seismicity. The earthquake recurrence parameters were computed for each seismic source zone based upon the doubly truncated exponential model. And an alternative ground-motion prediction relationship are selected for each seismic source zone and weighted to account for the epistemic uncertainty. The seismic hazard assessment for Arabian Plate is computed for 2% and 10% probabilities of exceedance in 50 years (corresponding to return periods of 2475 and 475 years). Maps showing spectral acceleration values as well as peak ground acceleration (PGA) are presented. The results were also displayed in terms of hazard curves and uniform hazard spectra for rock sites at selected 26 cities within the Arabian plates. The ground-motion levels are also deaggregated at the same sites, in order to provide insight into which events are the most important for hazard estimation. Deaggregation of PSHA results, classified the 26 cities into five groups shows the contribution of proximal or distant earthquake sources to the hazard. Seismic hazard maps show hazard level of relative variability among the selected cities with a trend of contour increases constantly from the center of the Plate to the edge side where the main plate boundaries are located.
