Vol 17, No 3 (2023)

For the first time, the results of petrophysical studies of the Bezymianny volcano extrusive rocks from dacites to andesites are presented. A comparative characteristic of the extrusive rocks properties is given according to the selected age groups. The dynamics of changes in the properties of extrusion rocks depending on their age is shown: it is established that the older the rocks, the higher the indicators of their density, strength and elastic properties. The petrophysical features of the rocks of the extrusive domes and lava flows are compared. The applicability of petrophysical properties to clarify the genesis of rocks similar in petrographic characte-ristics, in particular, of extrusive and effusive origin, is substantiated.

The article presents new results of geological-stratigraphic and isotope-geochronological study of young lavas in the northeast part of the Javakheti Highland (Lesser Caucasus, Republic of Georgia). A valley lava river (Algeti flow) with a complex structure and total length about 55 km was described for the first time (no information about this valley lava river was previously published in the scientific literature). It was shown that a young magmatism in the northeast of the Javakheti area developed in the time interval of 3.2–1.5 Ma. Its early phase (3.19 ± 0.10 Ma) was marked by the formation of the longest (up to 100 km) valley lava river (Khrami flow), composed of basalts, among the similar geological objects known in the Lesser Caucasus. Subsequently (2.7–2.5 Ma), the continuation of eruptions led to the formation of extensive lava plateaus in the region (Tsalka, Gomareti and others). The formation of the Algeti valley lava river (Algeti flow), composed of basaltoids, began from the end of Piacenzian and continued over ~1 m.y. until the beginning of Gelasian (2.7–2.0 Ma) as a result of the activity of volcanoes in the northern part of the Javakheti Range. The final stage of formation (1.9–1.5 Ma) of Algeti flow was likely associated with eruptions of volcanic cones near Tabatskuri Lake. The obtained data, along with the reconstruction of the history of young magmatism, made it possible to follow the main features in the formation of modern relief and the river valley system in the considered part of the Lesser Caucasus.

The paper presents the results of mathematical modeling of the stress-strain state of the epicentral zone before and after the strong earthquakes M_w = 6.4 of June 22, 2002 in the north-west of Iran in the region Qazvin and 26 January 2001 in India with M = 6.9. The method of modeling of the stress-strain state of the block elastic-isotropic heterogeneous medium disturbed by the system of faults under the influence of the external field of tectonic stresses was used, boundary conditions were set according to seismological data. It is shown that at a certain ratio between the main stresses the epicenters of strong cow earthquakes are localized in the area of high concentration of stress intensity. The development of aftershock process is caused by stress release caused by a new break, and the emerging clusters of aftershocks spatially correlate with the zone of released intensity of stresses. It is assumed that the tectonic rupture propagates in the direction of the zones of high intensity of stresses. The actual correlation between the rupture length and the earthquake magnitude from the accumulated elastic energy and its possible realization under given structural and tectonic conditions is shown.