Speaker
Mrs
Aurelia Hubert-Ferrari
(Université de Liège)
Description
The North and East Anatolian Faults in Turkey are two large conjugate strike-slip faults characterized by earthquakes of magnitude equal or larger than 7 and creep, which makes it difficult to evaluate their long-term seismic activity and the related seismic hazard.
The North Anatolian Fault (NAF) ruptured from east to west in a westward propagating sequence of M> 7 earthquakes since 1939 and is characterized by partial creep in its central segment since its rupture. Its activity was recorded in historical document studies over more than 1000 years, and in a number of paleoseismological studies. Their compilation (Frasers et al., 2010) evidences different pattern of fault ruptures along strike. The western transtensional section displays short recurrence intervals and switching between furcated fault strands. The central translational section shows a normal earthquake distribution and ruptures in unison or in close succession. The role of creep has yet to be evaluated, but this segment displays a very weak relation between accumulated strain and displacement. The eastern transpressional segment more closely interacting with the East Anatolian Fault (EAF) and the indenting Arabian plate shows a bimodal distribution.
The EAF was active during the 19th century according to historical documents and was mostly quiet during the 20th century. An Insar study (Cavalié and Jónsson, 2014) suggests full creep along its central part. Its historical record of earthquake is slightly less extensive than along the NAF, but still covers ~1000 years. Yet the EAF has been poorly studied. In particular, its paleoseismological record is very scarce, except near Hazar Lake located along the central creeping segments of the EAF. Paleoseismological trenches east of the Lake evidence only one event in the last 5500 years on the master fault and recurring ruptures along a close splay fault (Cetin et al., 2003). Several evidences of strong seismic shaking (i.e. ball and pillows, paleoliquefactions and fracturing linked to lateral spreading) were documented in the alluvial sediments of the large delta at the southwestern end of the Hazar Lake and their timing could correspond to destructive historical events (Hubert-Ferrari et al, 2017). Finally seismoturbidites in the deep lacustrine sediments attest for repeated clustered paleoshaking. The integration of historical and paleoseismological studies with Insar results rises questions about the long-term creep along the EAF and the role of splay faults. A long record of paleoruptures evidences in paleoseismological trenches along the principal displacement zone is needed to understand the long-term behavior of this fault. Such a study could have an impact on out understanding of seismic versus aseismic motion on large continental strike-slip faults.
Primary author
Mrs
Aurelia Hubert-Ferrari
(Université de Liège)
Co-authors
Dr
Ulas Avsar
(Middle East Technical University, Faculty of Engineering, Geological Engineering, Ankara)
Dr
Ziyadin Cakir
(Eurasian Institute of Earth Sciences, Istanbul Technical university, Turkey)
