Stress–Strain State of the Earth’s Crust in the Central Caucasus

Abstract

The Caucasus is a region of continental collision between Eurasia and Arabia and one of the Earth’s most seismically active and rapidly deformed continental regions. The wide range of deformation processes occurring in this relatively limited region makes the Caucasus as a whole and its central parts in particular a unique test area, the study of which can improve our understanding of the complexities of the stress–strain state, as well as the associated seismicity. During the instrumental period of observations, many strong earthquakes have been recorded here, e.g., the August 4, 1974 Bezhta earthquake (Mb = 5.4), the 1978 earthquake with a magnitude of 5.7, the February 23, 1981 Gavaz earthquake (Mb = 5), the October 12, 1992 Barisakho earthquake (Mb = 6.1), and the July 5, 2012 Zaqatala (Mb = 5.7). We have constructed the mechanisms of strong earthquakes and compared the results with the tectonic conditions of the studied region. Based on a morphostructural analysis of the modern relief of the central and eastern Greater Caucasus, a diagram of its morphostructural blocks has been compiled. The average earthquake mechanisms were constructed for the distinguished blocks, the prevailing types of slip in earthquake sources in each selected block were identified, and the fault kinematics were reconstructed. The solution was based on generally accepted tectonophysical theoretical views, with the wide application of modern structural–geomorphological methods, modern GIS technologies, and morphological analysis of the modern relief of this region. The modern tectonic stress field was reconstructed based on seismological data on earthquakes recorded during the entire instrumental period (1971–2019).