## 2 Tectonic Setting and Seismicity  
The Zagros mountain range in southwest Iran (Figure 1a) expanded from \(\sim\)250 km to \(\sim\)400 km in width and \(\sim\)1500 km in length from SE Turkey (in the west) to the Hormuz Strait (in the east) (Figure 1). This range was formed in a series of tectonic events related to the collision of the Arabian plate with the Eurasia plate in the Miocene [45; 46]. The Main Zagros Reverse Fault (MZRF) and MRF delineate the Arabia-Eurasia suture that limits the northern extension of the Zagros range (Figure 3) [16]. Figure 2: The sources of earthquakes catalogue and geological map: (**a**) seismotectonic map of northeastern Lorestan; (**b**) northeastern Lorestan geology map overlaid on a shaded relief map of the 10 m digital elevation model with active fault traces resulting from the Landsat images and field observations. The main structural features of the Zagros and its evolution history are known by various researchers [16,45,47]. During the Arabia-Eurasia collisional process, the sedimentary rock units in the northern domain of the Arabian plate have been folded and detached from its Pan-African basement into a long belt (Zagros fold-thrust belt). To the north of the Zagros fold-thrust belt and parallel to it is the Sanandaj-Sirjan Zone, and the Urumieh-Dokhtar magmatic arc, which consists of imbricated sedimentary and metamorphic rocks, and Andean-type volcanic rocks, respectively [47]. The abduction of the Neo-Tethys oceanic crust onto the northern margin of the Arabian plate in the late Cretaceous has been the first tectonic event in the development of the Zagros orogenic belt. In the late Campanian, the abduction finished while remains of the Neo-Tethys oceanic crust continued to subduct beneath Central Iran in the Oligocene-Moocene. Based on the NUVEL-1A plate motion model [28], currently, the collisional stage is active with a convergence rate of \(\sim\)30 mm/yr in the north-south direction. However, the GPS proposed a velocity of \(\sim\)20 mm/yr of the Arabian plate related to Central Iran [25]. The GPS indicates about half of the convergence is consumed by Zagros. The rates of convergence along the Zagros belt are seen to be continuously decreasing from SE to NW, from \(\sim\)9 mm/yr in SE Zagros to \(\sim\)6 mm/yr and \(\sim\)4 mm/yr in Central and N Zagros, respectively. The multisegmented Zagros Main Recent fault is a major NW-SE-trending right-lateral strike-slip seismic fault zone of more than 800 km long located between the Zagros fold-and-thrust belt in the southwest and Central Iranian range-and-basin in the north-east [16,20,32]. The fault trace in the northern margin of the Zagros range depicted by [PERSON] and [PERSON] [48] is equivalent to what is now known as the MRF, but there was no field evidence for the strike-slip component; only vertical displacements were observed (north-east side down). The MRF is divided into five major segments (from Kamyaran to Arjanak), including the Doroud, Nahavand, Garun, Sahneh, and Morvarid segments [32] (Figure 3). In the last century, several destructive earthquakes, such as Silakhorin 1909.01.23 with Mw7.3; Razan 1955.12.04, UTC: 14:02, epicenter: 33.50 N-48.80 E Ms 6.0; Heydarabad 1961.10.28, UTC: 10:46:33.54 N-48.49 E and Ms 5.0; Sahneh 1958.08.14, UTC: 15:26 and Ms 5.5; Nahavand 1958.08.16, Mw 6.6, UTC: 19:13 and epicenter: 34.25 N-47.84 E; Dinevar 1958.09.21, UTC: 16:18 and Mw 5.2; 1987.05.29, epicenter: 34.06 N-48.28 E, Ms 6.5 and Night/Wednesday; Farisneh 1957.12.13 with Mw 6.5; Nevahand 1958.08.16 with Mw = 6.7; Karkaneh 1963.03.24, UTC: 12:44, epicenter: 34.43 N-47.89 E and Mw 5.8; and Chalencholan 2006.03.31 with Mw = 6.1, have occurred on these segments (Figure 3) [25]. The most destructive was the 1909 earthquake (Ms 7.4) associated with a fault rupture over  
Figure 3: Seismicity and structure of the Zagros Main Recent Fault (MRF). The most recent and active structure (MRF) with its main segments is shown on the map.