Mechanism of young deformation in Tehran plain: a combination of field observation and analog modeling

The capital city of Tehran is located to the south of central Alborz. The North Tehran
fault, as the main structure of this region, perched on the northern part of the city
and separate alluvial fans from volcanic rocks of the Alborz. There are several other
faults within the city which seem to be structurally related to the North Tehran fault.
Geomorphic study of fans and river deposits suggest that most of these faults are active
and taking up both left-lateral and shortening in a wider zone to the south of North
Tehran fault. In addition to faults there is distinct folding within the Tehran plain. Field
observation along road cuts which cross these structures suggest that young folding in
Tehran plain are active and escalate due to the activities of the underlying faults. There is
little evidence of rupture in front of these structures and thus most of them are considered
as blind faulting. The trend of these structures is oblique to the North Tehran fault which
is probably due to distribution of left lateral deformation in wider zone within the Tehran
plain. The distance between active folds and the North Tehran fault increase from west
to east. Analog modelings were carried out to study the effect of thickness and slop of
deposits on position and trend of structures within the Tehran plain. Results from these
experiences show that geometry, orientation and distance between structures is probably
controlled by oblique shortening of the zone, as well as increase in thickness and slope
of the sedimentary deposits.