## 6 Discussion  
The geomorphologic features of the strike-slip fault system along the MRF zone and their effects on the outcrop patterns of lithological units, rivers, and gullies show the recent right-lateral strike-slip motion and activity of the MRF. Active tectonics of this fault have also caused large earthquakes. Considering recent activities along the DF, as described above, it is important to conduct an accurate evaluation of the slip rate and offset on this active fault; regarding the geological markers, rivers, and gullies, the maximum offset on the DF is about 775 m, which may be observed as a right-lateral motion displacement of the river in south Bagh-Lotfian in the southern segment of DF. However, there is clear morpho-tectonic evidence related to the late Pleistocene-Holocene activity of the Doroud Fault on satellite images. So far, many studies have been carried out to estimate the slip rate on the Main Recent Fault: [PERSON] and [PERSON] (2018) and [PERSON] et al. (2018) suggested 10-17 and 4-6 mm/yr, respectively; [PERSON] et al. (2018) 10 mm/yr; [PERSON] and [PERSON] (2018) and [PERSON] et al. (2018) 2-5 and 3 mm/yr slip rate, respectively; [PERSON] et al. (2018) 3.5-12.5 mm/yr; [PERSON] (2018), using GPS velocities, expanded a three-dimensional mechanical model containing pre-existing faults with frictional properties and suggested a long-term slip rate for the MRF (~2.3 mm/yr); and [PERSON] et al. (2018) estimated 1.6-3.2 mm/yr. Our work is the first slip rate study along the Doroud Fault. To determine the slip rate in the middle segment of the Doroud Fault, GPS RTK data were utilized (discussed in Section 4). We conclude that the average cumulative dextral offset, horizontal and vertical, on the Doroud Fault are about 10.5 m and 5.7 m, respectively, leading to a slip rate, horizontal and vertical, of about 2.28 \(\pm\) 0.42 mm/yr and 1.29 \(\pm\) 0.23 mm/yr, respectively. Our work is the first paleoseismological study along the Doroud Fault. The Darbe-Astaneh trench site is located near the epicenter of the 1909 earthquake with the mapped rupture (Figure 4). This site was selected based on remote sensing and field observations for its relatively high sedimentary potential. It delivered well-expressed surface deformation and adequate deposits for age determinations. This paleoseismic investigation along the Doroud Fault demonstrates the occurrence of several large, infrequent, and irregular earthquakes. Indeed, in our trench, nine paleoearthquakes were identified; the fault hosted at least eight large (Mw \(\sim\)5.5) earthquakes within the last 8375 \(\pm\) 35 Cal BP, and one older earthquake probably before some 66.62 \(\pm\) 5 ka, and the youngest occurred at 1250 \(\pm\) 25 Cal BP. Indeed, the fault hosted four earthquakes of more than Mw \(\sim\)7 and four of more than Mw \(\sim\)6 within the last 66.62 \(\pm\) 5 ka. The occurrence of seven seismic events within a short time interval may indicate that the seismic behavior of the Doroud Fault can be characterized by the clustering of earthquakes. Figure 17 is a time diagram that summarizes the observations from our trenching studies. The occurrences of seven large earthquakes during the last \(\sim\)3.3 ka, with a magnitude of more than an Mw which can be attributed to \(\sim\)6, suggest that the Doroud Fault could be characterized by a clustering of events (A). The two oldest events of the nine events identified occurred at 8350 \(\pm\) 35 to 66.62 \(\pm\) 5 ka, respectively, in the absence of macroseismic activity in the time interval between 3260 Cal BP to 8350 Cal BP, and in the time interval between 8350 Cal BP and 66 ka, two seismic gaps are observed, which can be attributed to a high rate of erosion, sedimentation, or unconformity. In paleoseismology, the non-preservation of sedimentary records is a recognized issue that can affect the identification of seismic events.