Shear wave splitting in a young continent‐continent collision: An example from Eastern Turkey

Abstract

We have determined the shear wave splitting fast polarization direction and delay time using data from the ETSE broadband experiment (Eastern Turkey Seismic Experiment), a deployment of 29 broadband seismic stations across the collision zone of the Arabian, Eurasian, and Anatolian plates. Our results show that the fast polarization directions are relatively uniform and they exhibit primarily NE–SW orientations. No abrupt changes in anisotropy directions are observed across the main tectonic units in the region: the Bitlis Suture (BS) and the North and Eastern Anatolian Fault zones. The fast polarization directions are determined to be sub‐parallel to the Anatolian, Arabian, and Eurasian absolute plate velocities, except for those stations in the northeastern corner of the Anatolian Plateau. Observed delay times range from 0.7 to 2.0 seconds with an average value of 1.0 second; the largest values are within the northern Anatolian Plateau which is underlain by an exceptionally low velocity zone in the uppermost mantle. We interpret shear wave splitting as the vector difference of the Eurasian lithosphere and northeastern or southwestern directed flow of the asthenospheric mantle. Comparisons of the polarization anisotropy with measurements of Pn azimuthal anisotropy suggest vertical anisotropic layering except in those areas which are underlain by partially molten uppermost mantle.

Lithospheric structure and the isostatic state of Eastern Anatolia: Insight from gravity data modelling

“…The results of the project suggested that mantle lithosphere is either absent or extremely thin beneath the eastern Anatolian Plateau (AlLazki et al, 2003;Gök et al, 2003;Sandvol et al, 2003). The thickness of the lithospheric mantle in the Eastern Anatolian region is ~60 km (e.g., Pearce et al, 1990;Al-Lazki et al, 2003;Gök et al, 2003;Sandvol et al, 2003). This is much less than the 100-125 km thickness of the cold and stable mantle lithosphere in the Arabian Shield and Iranian Plateau (e.g., Angus et al, 2006).…”

Crust-mantle mechanical coupling in Eastern Mediterranean and Eastern Turkey

“…The recorded delay time between these two components is a function of the severity of the anisotopy and the thickness of the anisotropic layer. The shear wave anisotropy studies that I use here are representative down to a depth of around 200 km or more in eastern Turkey (34) and the eastern part of NAFZ (35) being possibly shallower farther west (36). P n waves, on the other hand, propagate typically below the Moho discontinuity along approximately horizontal rays apart from source and receiver legs.…”

“…Therefore, it is more meaningful to compare the P n anisotropy directions with geodetically measured strain rates rather than velocities [see (40) for a study in which P n anisotropy is used to measure the width of mantle deformation across a Continental Transform]. In my analysis, I use the SKS fast-splitting directions from (34)(35)(36)41) for the Aegean, central and eastern parts of the NAF, eastern Turkey, and Dead Sea Transform, respectively (see Fig. 2).…”

Doğu Anadolu Bölgesi̇’ndeki̇ Kabuk Yapisinin Düşey Ve Yatay Yönlü Anali̇zi̇

“…In the evaluation of the region, the marine and continental basins have significant roles. The seismological studies (Al-Lazki et al, 2003;Türkelli et al, 2003;Sandvol et al, 2003aSandvol et al, , 2003bZor et al, 2003) realized for characterizing the compressional zone of the region and defining the geodynamics of the compression since 2003, the evolution was explained in the light of the studies and the presence of asthenospheric upwelling was determined (fiengör et al, 2003;Keskin 2003Keskin , 2007. It is expected that this upwelling causes to reduce the density of the subsurface formation with the effect of the high temperature and accordingly, brings along the reduction on values of the gravity anomalies.…”