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High-Resolution Seismic Velocity and Attenuation Models of the Caucasus-Caspian Region

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Conference paper

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The Caucasus-Caspian region is part of the Alpine-Himalayan collision belt and is an area of complex structure accompanied by large variations in seismic wave velocities. Using data from 29 new broadband seismic stations in the region as well as data from a temporary 1999-2001 deployment in eastern Turkey, a unified velocity structure is developed using teleseismic receiver functions and surface waves. Joint inversion of surface wave group dispersion curves generated from ambient noise with receiver functions show that crustal thickness varies from 34 to 52 km in the region. The thickest crust is in Lesser Caucasus and the thinnest is in the Arabian Plate. Thin crust is also observed near the Caspian. The lithospheric mantle in the Greater Caucasus and the Kura depression is faster than the Anatolian Plateau and Lesser Caucasus. This possibly indicates the presence of cold lithosphere. The lower crust is slowest in the northeastern part of the Anatolian Plateau where Holocene volcanoes are located. Fundamental mode Rayleigh wave phase velocities are determined at periods between 20 and 145 seconds. We observe a relatively high-velocity zone located in the upper mantle under the Kura basin and the western part of Caspian Sea that is continuous to the Moho. The images show very low velocities beneath the eastern Anatolian plateau implying the existence of a partially molten asthenospheric material underlying a very thin lithosphere. Using a two-station method, both Lg and Pg attenuation is measured and tomograpically inverted to yield attenuation maps. Efficient Lg propagation is observed throughout much of the Arabian plate. Moderate Lg Q is observed in the Lesser Caucasus and Kura Basin while low Lg Q is observed in the East Anatolian plateau. Pg shows highly variable propagation throughout the region.

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  • Seismology

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