High-Resolution Seismic Velocity Model of the Caucasus-Caspian Region (original) (raw)

Abstract

ABSTRACT 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. Despite the complexity of the region little is known about the lithospheric structure. Using data from 25 new broadband seismic stations in the region, a unified velocity structure is developed using teleseismic receiver functions and surface waves. Several distinct regions are recognized: the Greater Caucasus, the lesser Caucasus and the Caspian/Kura Depression. Depth(h)-Vp/Vs(k) stacks of the receiver functions suggest crustal thicknesses of 45-50 km in the Lesser and Greater Caucasus with relatively high crustal velocities (Vs=3.4 km/s). Variations of the receiver functions with back-azimuth indicate 3D variations in structure in the Greater Caucasus. Crustal thickness in the Kura Depression and at the edge of the Caspian is less well constrained due to pronounced multiples associated with thick sedimentary layers but the preferred results suggest a Moho depth of 38 to 48 km and lower crustal velocities (Vs=3.1 km/s). Love and Rayleigh surface waves dispersion curves have been derived from using both event-based analysis and ambient noise correlation. Short-period surface waves outline the sedimentary structure of the region, while longer periods highlight crustal velocity, crustal thickness, and upper mantle velocity. Joint inversion of the receiver functions with the surface wave dispersion curves to determine absolute shear wave velocity is ongoing.

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