Landslides near Enguri dam (Caucasus, Georgia) and possible seismotectonic effects

The Enguri dam and water reservoir, nested in the southwestern Caucasus (Republic of Georgia), are surrounded by steep mountain slopes. At a distance of 2.5&thinsp;km from the dam, a mountain ridge along the reservoir is affected by active deformations with a double vergence. The western slope, directly facing the reservoir, has deformations that affect a subaerial area of 1.2&thinsp;km2. The head scarp affects the Jvari–Khaishi–Mestia main road with offsets of man-made features that indicate slip rates of 2–9&thinsp;cm&thinsp;yr−1. Static, pseudostatic and Newmark analyses, based on field and seismological data, suggest different unstable rock volumes based on the environmental conditions. An important effect of variation of the water table is shown, as well as the possible destabilization of the slope following seismic shaking, compatible with the expected local peak ground acceleration. This worst-case scenario corresponds to an unstable volume on the order of up to 48±12×106&thinsp;m3. The opposite, eastern slope of the same mountain ridge is also affected by wide deformation affecting an area of 0.37&thinsp;km2. Here, field data indicate 2–5&thinsp;cm&thinsp;yr−1 of slip rates. All this evidence is interpreted as resulting from two similar landslides, whose possible causes are discussed, comprising seismic triggering, mountain rapid uplift, river erosion and lake variations.</p

Peculiarities of formation of catastrophic debris-flows in the basin of river Duruji (Eastern Georgia)

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Variation of Radiocarbon Content in Tree Rings During the Maunder Minimum of Solar Activity

We present here annual data on 14C abundance in tree rings during the Maunder minimum of solar activity (AD 1645–1715). We show that the solar modulation persisted during the minimum. We also compare these data with measurements of 10Be concentration in dated polar ice cores and with records of aurorae recurrence during this time interval.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Reconstruction of a reference subsoil model for the seismic microzonation of gori (Georgia): A procedure based on principal component analysis (PCA)

This article focuses on the full exploitation of geological and economically viable geophysical surveys for the seismic characterization of the shallow subsoil in the frame of microzonation studies in urban areas where economic resources for detailed seismic response analyses are scarce. In these conditions, the outcomes of inexpensive geophysical surveys (e.g., based on ambient vibration monitoring or surface-wave prospecting) must be fully exploited. To reduce the uncertainties related to these kinds of procedures, their joint interpretation in the light of geological evidence is mandatory. To this purpose, we propose the application of principal component analysis to combine the results of distributed singlestation ambient vibration measurements (horizontal-to-vertical spectral ratio [HVSR] technique) to provide a preliminary zonation of the study area. The zones identified in this way are then characterized by considering the available geognostic boreholes, VS profiles deduced by the joint inversion of HVSR curves, and available Rayleigh-wave dispersion curves deduced from active seismic prospecting (multichannel analysis of surface-waves technique). The final outcome allows the definition of a preliminary seismic model of the study area, which is also constrained by the available geological data deduced from on-purpose surveys. The proposed approach has been applied to the city of Gori (Georgia). The proposed approach allowed a reliable assessment of buried geometries, geological domains, and the distribution of lithofacies, which can control the local seismic response. In detail, the major role of paleovalley infills and interfluve domains has been enlightened by adding in evidence concerning the peculiar stratigraphic relationships and buried morphologies, which may determine 1D and 2D resonance effects