The 20 June 1990 Rudbar earthquake, Mw 7.3, occurred within a rugged mountainous region causing ~80 km long surface rupture along the Rudbar fault. The earthquake occurred on a NW-striking (~N290º-300º) fault plane with nearly pure sinistral kinematic but shows a complex surface deformation along Zard-Goli and Kabateh segments with reports of normal and reverse movement components. To find how the pure sinistral mechanism at depth could produce the complex surface deformation, we calculate the state of present-day stress by inversion of earthquake’s focal mechanisms and also do detail mapping of the earthquake surface rupture using Google Earth images and Optical Image Correlation derived deformation maps. The stress inversion suggests an axis of horizontal maximum stress within N248º-N260º. Our new detailed map of the surface rupture reveals that the rupture along the Zard-Goli and Kabateh segments dominantly include array of minor right stepping en-echelon faults (N260º to N295º striking). It indicates that the orientations of the ruptures are partially parallel to the direction of maximum principal stress, thus resulting in the development of true normal movement component at the surface.