Tectono-Geodynamic model of the earthquake’s foci zones of the southern slope of the Greater Caucasus (within Azerbaijan)

At the present stage of tectogenesis, the southern slope of the Greater Caucasus reveals itself by relatively higher seismic activity within Azerbaijan territory, where more than 80 earthquakes with M ≥ 4 took place over the past century, whereas 20 of them was with M ≥ 5. Seismic activity in this region is associated with ongoing, intense structural restructuring here with significant amplitudes of recent movements in the underthrust-thrust interaction zone of the South and North Caucasian continental blocks (microplates) within the boundaries of the collisional interaction of the Eurasian and Afro-Arabian continents. The Earth crust of the region is characterized by tectonic heterogeneity, expressed by the complex relationships between its constituent structural-formational units with different lithological-stratigraphic sections, deformation patterns, and geological development history.

With this study we analyze active tectonics of the region from the viewpoint of the mechanism of the ongoing pseudosubduction process within convergence zone of the south and north Caucasian microplates. We have also analyzed and interpreted seismological data along with GPS monitoring results in relation to geodynamic activity with determining of correlations with deep structure peculiarities. An analysis of the distribution of earthquake foci indicates the existence of structural-dynamic relationships between them and subvertical and subhorizontal contacts in the earth's crust.   During the continental stage of Alpine tectogenesis (since the end of the Miocene), intensive lateral compression process was caused by intrusion of the frontal wedge of the Arabian indenter into the buffer structures of the southern frame of Eurasia. This geodynamic phenomenon is actual also for present day time. This fact evidenced by GPS measurements on recent geodynamic activity, which demonstrates intensive (up to 20 mm/year) movement of the Southern Caucasus block toward Northern Caucasus microplate. It is suggested that this process led to observed seismic activity from historical period, where the earthquakes occurred mainly in the southern slope’s accretionary prism area and the adjacent strip of the Southern Caucasus microplate.  

Likewise, we also analyzed and correlated some range of strong (M>5.0) seismic events that occurred within study area until 2026, involving their fault plane solutions. The focal mechanisms of the earthquakes reveal various types of mechanisms, but mostly near-vertical, normal and strike-slip faulting mechanisms. As a result of our study, we have also generated a digital 3-D tectonic-geodynamic model of the geological environment along with earthquakes’ in-depth distribution, which in turn explains from geological point of view the causes of ongoing seismic activity within study area.