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    Mosha Fault:

The Mosha fault is one of the major active faults in Central Alborz (Figure 1) as shown by its strong historical seismicity and its obvious morphological signature. Situated at the vicinity of Tehran city, this ~150 km long ~N100E trending fault represents an important potential seismic source that threatens the Iranian metropolis. Our investigations within the Tar Lake valley, along the eastern part of the fault – potentially the site of the 1665 (VII, 6.5) historical earthquake - allows us to calculate a preliminary 2.2 ± 0.5 mm/yr minimum left lateral slip rate(Ritz et al.,2003). If we assume a characteristic coseismic average displacement comprised between 0.35 m (Mw 6.5) and 1.2 m (Mw 7.1) – calculated from Wells & Coppersmith’s functions (1994) and taking the moment magnitudes attributed to the 1665 and 1830 earthquakes (e.g. Berberian & Yeats, 2001) – the mean maximum recurrence intervals along this segment of the Mosha fault are comprised between 160 and 620 yrs