THE SEGMENT STRUCTURE OF SOUTHERN BRANCH OF THE NORTH ANATOLIAN FAULT AND PALEOSEISMOLOGICAL BEHAVIOUR OF THE GEMLİK FAULT, NW ANATOLIA

Indexed In

Volume 147 / 2013

Authors:

Selim ÖZALP, Ömer EMRE, Ahmet DOĞAN

Keywords:

North Anatolian Fault-Southern Branch, Gemlik Fault, paleoseismology.

Abstract:

The North Anatolian Fault (NAF), which is an intra-continental transform fault, is divided
into two branches as Northern and Southern branches in Marmara Region. The southern
branch which separates from each other by rightward stepovers between Bandırma and
Dokurcun valley is formed by three main fault segments as Geyve, İznik and Gemlik from
East to West. The length of fault segments ranges between 40 and 57 km and GPS data in
Southern branch propose a 5 mm/year slip rate. Two surface faulting events were observed
during paleoseismological excavations which had been carried out on 40 km long Gemlik
segment and these can be correlated with earthquakes that occurred in 1857 and 1419. The
recurrence interval between the last two earthquakes in Gemlik Fault is 438 years. Findings
indicate that Gemlik fault was also included into surface faulting of the earthquake in
1419 which its presence is known in İznik fault. At least 95 km long multi-segment surface
faulting developed in this earthquake. Based on 5 mm/years slip rate, the cumulative offset
amount slip rate of NAF was approximately estimated as 3 meters in 595 years in region
between İznik Lake and Dokurcun Valley. Accordingly; it can be stated that the southern
branch of the North Anatolian Fault has a potential to trigger a large earthquake as well
as the Northern branch.