The Alborz Range, northern Iran, is a chain of mountains along the southern side of the Caspian Sea. This mountain range shows strong tectonic activity with several destructive earthquakes in the past. The range is tectonically active, and the seismicity record shows both range-parallel left-lateral and thrust faulting. Tehran the capital of Iran and one of the largest cities in the world is located in the foothill of the Alborz Mountains, which is at risk of seismic hazard. This study is mainly focused on a scarp that passes by west of the Qarchak (a suburb in south east of Tehran) and therefore it is called the West Qarchak Fault. So, geological and geophysical surveying method was applied to study the West Qarchak Fault which is continuous and reaches to Pishva Fault in south east (with same trend) and crosses the Kahrizak Fault in the north west. In conclusion, it can be seen that apparently the geometry of the West Qarchak Fault is normal but the real mechanism is reverse (based on subsurface investigation). Morphologically, the Kahrizak Fault scarp has some similarity to the West Qarchak fault and it can be said that the geometry and mechanism of the Kahrizak Fault is same as the West Qarchak Fault, but requires a more detailed study.
