ساختارهاي خطي جنوب تهران (سري گسل هاي ري- كهريزك): پرتگاه گسل يا پديده اي زمين ريخت شناختي؟!

Linear Structures in South of Tehran (Reys and Kahrizak "Faults"): Fault Scarps or Geomorphologic Phenomenon?!

Tehran and its surrounding region are within affecting zone of some active faults of North Tehran and Mosha in north-north east and Parchin and Pishva in south. In addition, there are some other shorter faults and linear markers within the urban area of Tehran such as Niavaran, Mahmoudieh and Davoudieh faults in the northern part of city, and Rey and Kahrizak scarps in the south. Previously, according to occurrence of several historical earthquakes in Rey area and also some geomorphologic evidences, most of these markers with the linear scarps in south Tehran alluviums were mentioned as active faults. From seismotectonic and urban geology point of view whether these faults exist or not are an important issue. Recent seismotectonic studies including paleoseismology and geophysics investigations have failed to prove existence of such faults beneath the observed surface scarps. So in this paper according to delivered data from our paleoseismology, geophysical and seismotectonic investigations and also some geological evidences of foreland basin deposits (late Quaternary) in the Central Alborz (ex: shoreline evidences in Parchin area-south east of Tehran) and in some other place such Kordan fan (west of Karadj), we suggest that these scarps may be a kind of shoreline in front of the Tehran piedmont or the actual faults may be in different place than that suggested by observation of surface escarps. In this research we use satellite imagery (Land Sat, Spot, Quick birds), aerial photos and GPS kinematics to do Digital Elevation Model (DEM) through the Kahrizak scarp with paleoseismology trenching and geophysical (Geoelectric and Georadar) investigations on different parts of Rey and Kahrizak scarps.