Tectonic Activities Description in the Ongoing Collision Zone of the Eurasia-Arabia Plates Using 2D Surface Waves Tomography

Abstract

In order to better understand the regional tectonic activities of the continent-continent ongoing collision-compressed edge zone of the Eurasian-Arabic plates, 2D tomography maps of the Caucasus territory using the Rayleigh waves were generated. The 2D tomography images of this study, illustrate the large variety in surface wave propagation velocity in different complex geologic units of the Caucasus. To draw the 2D tomography maps, we accomplished a 2D-linear inversion procedure on the Rayleigh wave dispersion curves for the periods of 5 to 70 s (depth= ~180 km). To conduct this, local-regional data from ~1300 earthquakes (M≥3.9) recorded by the 49 broadband stations from 1999 to 2018 in a wide area with complicated tectonic units were used. In comparison with results of previous studies in Caucasus, the tomography maps for the long-periods (T= 50-70 s; depth ~180 km) are more influenced by the velocity structure of the uppermost mantle which demonstrate the ultralow and ultrahigh-velocity anomalies. The results for the medium-periods (30≤T≤45 s), the low-velocity zones coincide with areas thought to be correlated with underplating of the lower crust (e.g. shallow LAB), while, the high-velocity zones are usually demonstrating the presence of a normal continental crust over a stable and thick or oceanic-like lid. Short-periods (5≤T≤25 s) are more influenced by the ever-evolving deformations of the geological units, sedimentary basins, volcanic complexes, uplifts, and reveals a low-velocity small zone, on the NW slope of the Aragats volcano (depth= ~7 km), which is different from the results of other studies.