Figure 4 . a ) Correlation between mainshock rupture (colored ellipses is the surface projection of rupture) and aftershocks of the first 45 days (filled circles). Stars are mainshock and largest aftershock hypocenters relocated in this study (section 3). The mainshock focal mechanism is obtained in section 2. The M4.1 27/05/2020 aftershock focal mechanism is from IRSC. Inner colors represent their depths. Faults are plotted with red lines. curved lines on the rupture model represent rupture direction. The square is the location of Mosha town. The dashed ellipses show the damaged areas of the Ms 5.2 1930 and Mb 4.0 1955 earthquakes (after Berberian et al., 1993). Other focal mechanisms are from microearthquakes on the MSH obtained by Tatar et al. (2012) from June to October 2006. The solid circle is the observed thermal area on the MSH (after Eskandari et al., (2018). b ) The directivity effect of the 7th May Mw5.1 mainshock observed from the PGA recorded in the triggered BHRC network stations in the region. Strong motion stations are shown in triangles. The black dashed rectangle shows the area shown in (c). (c) PGA distribution of the mainshock in the Tehran area. Solid lines are the active faults (after Talebian et al., (2016)). Strong motion stations inside Tehran city are shown in reverse triangles. Inner colors of triangles represent the maximum spectral frequency (Amax) at the stations. Dashed lines are probable shore-line scarps (after Nazari et al., 2010).