Deep Structure, Volcanic and Seismic Activity Regime in Elbrus Region

Abstract

According to obtained results of profiling by microseismic sounding method along the line in submeridional direction crossing the eastern cone of the Elbrus volcano and a magmatic chamber was found under the Elbrus volcano in the range of depths of 7‒13 km below sea level with horizontal size of ≈ 7 km. At the depths of 18‒40 km, a narrow linear magmatic focus steeply dipping in the southern direction is deduced, its horizontal size in the cross section is ≈5 km underlain by another magmatic focus at the depths of 45‒55 km, penetrating the upper mantle. The found magmatic chamber and earthquake center in the crust section are formed by isometric and linear low-velocity bodies. The sections of two profiles show deep faults correlated with morphological features revealed on the surface. To the south of Tyrnyauz town at the depths of 17‒40 km below sea level, a low-speed steeply sinking in the northern direction linear body was found and interpreted as cool volcanic channel approximately at the size of Elbrus. Having carried out geophysical research we obtained data on 7 ancient earthquakes with magnitude M = 6.5‒7.0 occurred over past 7000 years in the vicinity of the volcano. In that historic period five strong eruptions of Elbrus volcano had happened. We settled the absence of time commonality in activations of volcanism and seismicity. Currently Elbrus volcano is in a phase of deep seismic abate. In 2004‒2017 we have fulfilled geological, geophysical and paleoseismological research that confirms Elbrus is not completely extinct volcano.