The June 20th Mw 7.3 Rudbar earthquake happened on a left-lateral strike-slip fault with 80 km length along three main discontinuous right-stepping segments in western Alborz mountain belt. The sparse field measurements showed a horizontal and vertical displacement of ~60 cm and ~95 cm, respectively. The reported surface slip displacements are surprisingly low given the high moment release of the shallow event, coupled with the pure nearly vertical left-lateral fault. To fully resolve the coseismic displacement, we calculate the surface displacement field associated with the event using optical image correlation of satellite and aerial photos. The measured maximum fault parallel horizontal displacement of ~5.5 m in the eastern part of the fault, Zard-Geli segment, is in agreement with the macroseimic isoseismal curves. The minimum displacement happened on the beginning of Kabateh (~50 cm) and the end of Zard-Geli (~ 1.2 m). The average magnitude of surface slip is about 2.2 m which is in agreement with the reported moment of the event provided that the width of the fault plane be ~15 km. The larger surface displacement measured by the optical image processing method is due to the distribution of deformation over a wide fault zone with a width of ~300 m to ~1600 m. Moreover, we identify a new surface rupture of ~23 km length expanded from Sefid-Rude to the NE of Zard-Geli fault segment.