New Paleoseismological Results within the Overlap Zone of NW and SE Segments of North Tabriz Fault (NW Iran)

Tabriz city، the most highly population city of NW Iran، is located close to the North Tabriz Fault (NTF). This 150 km right-lateral strike-slip fault consists of two major fault segments arranged in right-stepping pattern. A pull-apart basin has been formed within the overlap zone of these fault segments due to the recent right-lateral motion. The basin margins mark by fault branches and fault splays، which connect these two major segments of NTF. High level historical earthquakes occurrence shows seismic activity of NTF. Among which، NTF is responsible of at least two destructive earthquakes occurred in 1721 A. D. (Ms 7. 3) and 1780 A. D. (Ms 7. 4). This fault has not experienced any strong seismic events since 1780 A. D. Within past decades، it has been tried to recognize large number of old earthquakes utilizing paleoseismological investigation. Previous paleoseismological studies have been focused on the NW and SE segments of the fault. In the present study، to complete the data sets necessary to assess the seismic hazard related to Tabriz city، we focus on overlap zone of the two main fault segments. Using aerial photos، satellite images and field investigations، a potential site has been recognized within the zone (6 km NW of Tabriz City) to perform paleoseismological studies. Trench opened perpendicular to fault scarp strike and focused paleoseismological investigations in that، show evidences of at least two macroseismic events.