Tomographic evidence of slab detachment beneath eastern Turkey and the Caucasus

Abstract

SUMMARY Teleseismic phase readings from the Eastern Turkey Seismic Experiment (ETSE) have been inverted using teleseismic tomography in order to create a 3‐D image of the underlying mantle beneath Eastern Turkey. The aim was to investigate the existence of an upper mantle negative velocity anomaly that is used to explain the uplift of Eastern Anatolian plateau and the potential pieces of detached oceanic slabs related to Neo‐Tethyan subduction suggested by previous studies. Using teleseismic waveforms from the 29 stations of the Eastern Turkey Seismic Experiment, 2926 direct P phases from 146 events were picked by using adaptive stacking techniques. In order to increase the station coverage and resolve the surrounding area, the phase readings from the International Seismological Center (ISC) Bulletin have also been added. The data set consists of 9571 P and PKP phase readings of 79 stations from 503 teleseismic events. This study develops the first high‐resolution 3‐D upper mantle P‐wave tomographic model for this region. The tomographic results show the existence of an upper mantle negative velocity anomaly to a depth of ∼200 km beneath the eastern Anatolian accreationary complex (EAAC) as commonly observed in the previous studies that suggest a shallow partially molten asthenosphere. The slab‐like high velocity anomalies beneath the EAAC, Pontides and Caucasus are interpreted as the detached southern and northern Neo‐Tethys slabs.

Thickness of the lithosphere beneath Turkey and surroundings from S-receiver functions

“…Recently, tomography studies by Biryol et al (2011) andFichtner et al (2013a) have confirmed that a hot and buoyant asthenospheric body supports the ∼ 2 km elevation of the Eastern Anatolian Plateau in the presence of an about 45 km thick crust (Şengör et al, 2003;Zor et al, 2003). At about 350 km depth, a fast anomaly has been found by tomographic studies and interpreted to represent a slab detachment (Lei and Zhao, 2007;Zor, 2008 Kalafat et al, 2008), NOA-Net, Aristotle University Thessaloniki (HT-Net) and GEOFON (Hanka and Kind, 1994;GEOFON Data Centre, 1993). We apply the S-receiver function method to this data set in order to image seismic discontinuities in the crust and upper mantle.…”

Recent behavior of the North Anatolian Fault: Insights from an integrated paleoseismological data set

“…Paleomagnetic directions in the west Anatolian extensional province are rotated clockwise [Piper et al, 2008], which we attribute to rotations associated with extension. The plate thickness in the east Anatolian contractional province is 40-50 km [Zor, 2008], in the central Anatolian Ova province 36-40 km thinning toward the southern edge [Zor, 2008], and in the west Anatolian extensional province spot thicknesses are generally in the range of 22-30 km [Tirel et al, 2004;Zhu et al, 2005], with a thickness of only 8 km in the Sea of Marmara [Bécel et al, 2009]. We assume that the thickness of the plate in the central Anatolian Ova province is approximately that of the whole region prior to the present tectonic regime (i.e., at least 13 Ma.).…”

Crustal S-wave structure around the Lake Van region (eastern Turkey) from interstation Rayleigh wave phase velocity analyses

“…By checking regional waves in the crust (L g ) and the upper mantle (S n ), they observed both waves disappearing through the Eastern Anatolian Plateau, coinciding with the zones of inefficient S n propagation, and heating of a thin to absent mantle. Zor's (2008) tomographic results showed that the negative velocity anomaly above the slab-like positive anomaly may be an upwelling hot asthenosphere in the upper mantle beneath Eastern Anatolia and brings about slow shear-wave velocity anomalies. A magnetotelluric study carried out in Eastern Anatolia by Türkoğlu et al (2008) showed that the upper mantle has a very low resistivity, which is related to the presence of shallow and partially molten material.…”

“…A vast volume of the volcanic activity in the Eastern Anatolia (~43,000 km 2 ) was produced after regional block uplift (11-13 Ma) and this process moved from the north in the Erzurum-Kars Plateau to the south-southeast in the Muş-Nemrut-Tendürek volcanoes (Keskin, 2007). Several different geodynamic models were created to explain the collision zone between the Arabian and Eurasian Plates (Şengör and Yılmaz, 1981;Dewey et al, 1986;Barazangi et al, 2006;Keskin, 2007;Zor, 2008;Gök et al, 2011;Skobeltsyn et al, 2014) and many of these were interpreted in detail by Keskin (2007). Şengör et al (2003) revealed that the East Anatolian High Plateau is deprived of mantle lithosphere, which is referred to break-off of northward subducted slab (started some 11 Ma ago) beneath the widespread melting due to direct contact with hot asthenosphere.…”

“…The Eastern Turkey Seismic Experiment (ETSE) project was performed by Sandvol et al (2003b) using the earthquake data of 29 V-shaped broadband PASSCAL stations in this region. Data recorded via these stations of this project have been used and processed by many authors with different methods , 2004Gök et al, 2003Gök et al, , 2007Sandvol et al, 2003a;Türkelli et al, 2003;Zor et al, 2003;Angus et al, 2006;Lei and Zhao, 2007;Özacar et al, 2008;Zor, 2008;Biryol et al, 2011;Gökalp, 2012;Delph et al, 2015b) and they have supplied new approaches for the 3-D crust and mantle dynamics of the region. Al-Lazki et al (2003) interpreted low (<7.8 km/s) Pn velocities under the Anatolian Plateau as most likely the absence of the mantle lid, just as AlLazki et al (2004) observed the same velocities at the broad-scale in eastern Turkey and surrounding regions associated with hot, unstable mantle lid zones and active volcanism starting from the Late Miocene.…”