# Probabilistic Seismic Hazard Assessment for United Arab Emirates, Qatar and Bahrain
## 4 The Considered Seismic Source Models  
The delimitation and characterization of the possible potential seismic sources in the region of interest is another key point for any PSHA [61; 64]. Area sources are usually used to delimit the distributed seismicity that could not be associated directly to active faults. In this regard, the estimated seismicity recurrence parameters are assumed to be uniform inside each individually defined source zone. When delineating the possible active source areas, all available information about geology and seismotectonics of the region (focal mechanisms and active faults), as well as seismicity (historical and instrumental), was taken into account [2; 64]. In the current assessment, and to consider the uncertainty in the source model, three alternative sets of recently published source models are used in a logic-tree scheme; one of them is a spatially-smoothed seismicity model, and the other two are the area source models developed by [PERSON] et al. [65] and [PERSON] et al. [2] for the Arabian Peninsula and the surroundings of the UAE (see Figure 2). The area source model by [PERSON] et al. [2] was developed specifically for the UAE and its surroundings. Using the previously quoted catalog [6], alongside with available data about active faults in the Zagros and the Makran regions [61], as well as the geology and crustal thickness information [66; 67], the authors proposed a new seismic source model consisting of a total of 12 area seismic sources. Those area sources can be categorized into two main groups: crustal shallow-depth (h \(\leq\) 35 km) area sources (from Sh-01 to Sh-10; see Figure 2a), and intermediate-depth (35 \(<\) h \(\leq\) 70 km) area sources (IN-01 and IN-02; see Figure 2b). The defined sources cover the possible potential active seismic regions that may contribute to the seismic hazard in the studied countries. The authors delimited the sources Sh-01 (Arabian Gulf), Sh-02 (Foredeep and Mountain Front), Sh-03 (Simple Fold Belt), Sh-04 (High Zagros Thrust Belt), and IN-01 (Zagros Intermediate-depth Earthquakes) to cover the seismicity along the ZBFTB. Additionally, the sources Sh-05 and Sh-06 were delimited specifically to cover the crustal shallow earthquakes along the Nayband-Gowk Fault zone and the Zagros-Makran Transition Zone, respectively (see Figure 2a,b). Furthermore, three different area sources were defined to delimit both crustal and intermediate-depth seismicity along the Makran Subduction Zone (Sh-07 \"Western Makran\", Sh-08 \"Eastern Makran\", and IN-02 \"Makran Intermediate-depth Earthquakes\"). The last shallow crustal area sources were delineated specifically to include the potential seismicity located within the Oman Mountains and Dibba Fault (Sh-09), and the Owen-Murray Fracture zone (Sh-10) (see Figure 2a,b) (for more information about the specific characteristics for each delimited area source, see [PERSON] et al. [2]). Similar to the Earthquake Model for the Middle East [60; 61], the [PERSON] et al. [2] seismic source model considers the intermediate-depth earthquakes as separate source areas. All related seismicity parameters (annual rate of earthquakes above Mw 4.0, \(b\)-value, mean seismogenic depth, and maximum recorded and expected magnitudes), as well as the mean stress regime for the defined seismic sources, have been imported and considered in the current assessment and tabulated in Table 3.  
A second alternative model is a spatially smoothed seismicity model. It was chosen to be used in the current assessment to consider the uncertainty in the knowledge of the boundaries of the previous zoning model, as well as to consider earthquakes where they really happen (e.g., low-magnitude earthquakes occurred in the Arabian cratonic area to the southwest from the defined sources). This model is based on the approach proposed by [PERSON] [68] to model the distributed seismicity, i.e., the seismicity that cannot be assigned to specific tectonic structures. The employed procedure is detailed on the following.