NEW_Accomplishments.indd - IRIS

SURFACE OF THE EARTH: GLOBAL STUDIES
2006 IRIS 5-YEAR PROPOSAL
The Eastern Turkey Seismic Experiment:
The Study of a Young Continent-Continent Collision
Eric Sandvol • University of Missouri
Niyazi Turkelli • Bogazici University, Istanbul, Turkey
Muawia Barazangi • Cornell University
During the last 10-20 million years the tectonics of Turkey and the Anatolian plateau can be described as the convergence
of three continental plates: the Anatolian, Arabian, and Eurasian plates form a diverse suite of tectonic boundaries. This
tectonic environment makes the East Anatolian plateau and Bitlis suture an excellent natural laboratory to study the early
stages of continental collision and its consequences. Until now, the only well-studied example for active continental collision
has been that of India colliding with Eurasia and the subsequent uplift of the Tibetan plateau.
In order to address these important questions,
the Eastern Turkey Seismic Experiment (ETSE)
was conducted across the East Anatolian plateau
and the northernmost Arabian plate. ETSE was
a 29 broadband station PASSCAL network that
was designed to improve our understanding of the
Bitlis/Zagros thrust zones, as well as the nature of
continental escape along the EAFZ and the North
Anatolian Fault Zone (NAFZ), through the imaging
of upper mantle and crustal structure. The
average station separation was approximately 50
km. The ETSE western traverse crosses a region
where it has been well documented that the
Anatolian block is escaping westward, while
the ETSE eastern traverse crosses a region
where the deformational regime is far more
complex.
The East Anatolian High Plateau is a
region of average ~2 km elevation exhibiting
active diffuse N-S shortening and widespread
Pliocene to recent volcanism. Its elevation was hitherto thought to result from a presumed crustal thickness of about 55 km.
Seismic data collected by ETSE have shown, however, that its maximum crustal thickness is only some 45-48 km (Zor et
al., 2003). Combined with tomographic models of regional seismic velocity and attenuation, this shows that most of the
East Anatolian High Plateau is devoid of mantle lithosphere (Al-Lazki et al., 2003; Gok et al., 2003). The absence of mantle
lithosphere is ascribed to break-off of northward subducted slab beneath the prism and the widespread volcanism to melting
its lower levels because of direct contact with hot asthenosphere. The East Anatolian High Plateau is thus supported not by
thick crust, but by hot mantle. The ETSE results offer a multi-disciplinary investigation of one of the earthʼs best examples of
ongoing continent-continent collision.
Al-Lazki, A., Sandvol, E., Seber, D., Turkelli, N., Mohamad, R., and Barazangi, M., Tomographic Pn velocity and anisotropy structure beneath the Anatolian
plateau (eastern Turkey) and the surrounding regions, Geophys. Res. Lett., 30, 8040, doi:10.1029/2003GL018912, 2003.
Gok, R., Sandvol, E., Turkelli, N., Seber, D., and Barazangi, M., Sn Attenuation in the Anatolian and Iranian Plateaus and Surrounding Regions, Geophys.
Res. Lett., 30, 8042, doi:10.1029/2003GL018912, 2003.
Orgulu, G., Ahktar, M., Sandvol, E., and Barazangi, M., The Seismotectonics of the Eastern Anatolian Plateau, Geophys. Res. Lett., 30, 8040, doi:10.1029/
2003GL018912, 2003.
Zor, E., Sandvol, E., Gurbuz, C., Turkelli, N., Seber, D., and Barazangi, M., The Crustal Structure of the East Anatolian Plateau from Receiver Functions,
Geophys. Res. Lett., 30, 8044, doi:10.1029/2003GL018912., 2003.
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