Crustal and Upper Mantle Structure of the Caucasus and Eastern Anatolia

Abstract:

In Greater Caucasus, Lesser Caucasus, and Eastern Anatolia, the ongoing Arabia-Eurasia collision has led to the highest mountain belt and one of the highest plateaus in Europe. The origin of this high topography is still subject of a debate. In order to help better understand the lithospheric and upper asthenospheric structure of this region, we applied Rayleigh Wave Two Plane Wave Tomography using the sensitivity kernels obtained with 1^stBorn approximation. 149 teleseismic events (M_w> 6.3) collected from 115 temporary broadband stations. These stations come from the CNET network including 15 Georgian National stations, 35 stations from Republican Seismological Survey Center (RSSC) of Azerbaijan and 32 stations from KOERI (Kandilli Observatory and Earthquake Research Institute). We also have used waveforms from the ETSE (Eastern Turkey Seismic Experiment) network and NISN (Northern Iraq Seismographic Network) stations recorded between 2007 and 2009. We obtained phase velocity variations for 13 different period bands between 142 to 20 s central period with the standard error estimate of 0.055 km/s of phase velocity. In addition, we estimate the azimuthal anisotropic component of these phase velocities. Low velocity anomalies are obtained around Eastern Anatolia for all the periods. We obtained high velocity anomalies between 111 to 20 s in the Black Sea region. Low velocity anomalies in this region are observed at 143 and 125 s may be the related with upwelling hot asthenosphere. High velocity anomalies are observed in Rioni Basin between 142 to 100 s. High velocity anomalies related with thick sedimentary layer in Kura basin are observed starting at 33 s. A constant high velocity body in North-East Iran may be interpreted as a remnant piece of subducted Arabian plate beneath Eurasia.