Teimuraz Matcharashvili

In this research, the results of the analysis of Enguri Large Dam (West Georgia) monitoring features, such as foundation displacement data and water level (WL) variation in the reservoir, were investigated. A statistical approach based on calculating time series helps us determine the research area’s dynamic picture. In this article, we have used various nonlinear analysis methods. Nonlinear dynamics of deformation and filling/reloading near grand dams reflect the complexity of the mentioned time series, connected with the natural agents (regional and local geodynamics), which were presented even before dam erection, and the effects of the water level variation in the reservoir. Both these effects are documented by observations from 1974 to 2024 at the Enguri Large Dam. Modern linear and nonlinear primarily data analysis techniques will be used for analysis of monitoring characteristics of the Enguri Large Dam: Kullback–Leibler divergence, mutual information, Shannon entropy, and Tsallis entropy. The obtained data on the dynamics of deformation and filling/reloading near a large dam can be used for the assessment of the possible risks connected with abrupt changes in the routine dynamics of construction.

One of the interesting directions of complexity theory is the investigation of the synchronization of mechanical behavior of large-scale systems by weak forcing, which is one of manifestations of nonlinearity/complexity of a system. The effect of periodic weak mechanical or electromagnetic forcing leading to synchronization was studied on the laboratory load–spring system as well as on a big dam’s strain data. Due to synchronization, the phase space structure of the forced system strongly depends on the weak forcing intensity–determinism show itself in the recurrence of definite states of the forced system. The nonlinear dynamics of tilts/strains/seismicity near grand dams reflect both the complexity of the mentioned time series, connected with the natural agents (regional and local geodynamics), which were presented even before dam erection, as well as the effects of the water level (WL) variation in the reservoir, which is a quasi-periodic forcing superimposed on the natural geodynamic background. Both these effects are documented by the almost half-century of observations at the large Enguri Dam. The obtained data on the dynamics of strain/seismicity near a large dam can be used for the assessment of the possible risks, connected with the abrupt change of routine dynamics of construction.

The 271 m high Enguri arch dam, still one of the highest arch dams in operation in the world, was built in the canyon of the Enguri river (West Georgia) in the 1970s. It is located in a zone of high seismicity (MSK intensity IX) and close to the Ingirishi active fault. The high seismic and geodynamical activities together with the large number of people living downstream of the dam make the Enguri dam a potential source of a major catastrophe in Georgia. Thus, the Enguri Dam with its 1 billion cubic meter water reservoir should be under permanent monitoring. At the same time, this area is an amazing natural laboratory, where one can investigate both tectonic and geotechnical strains and processes as well as their response to the lake load–unload impact (i.e., the reaction to a controllable loading of the Earth crust). This is an important scientific issue, connected with a fundamental problem of reservoir-induced earthquakes as well as with environmental geotechnical problems related to the safety of large dams. Application of nonlinear dynamics methods allows for the division of events, ordered by reservoir water regular strain impact from the background seismicity.

In the present work, we aim to analyse the regularity of a seismic process based on its spatial, temporal, and energetic characteristics. Increments of cumulative times, increments of cumulative distances, and increments of cumulative seismic energies are calculated from an earthquake catalogue for southern California from 1975 to 2017. As the method of analysis, we use the multivariate Mahalanobis distance calculation, combined with a surrogate data testing procedure that is often used for the testing of non-linear structures in complex data sets. Before analysing the dynamical features of the seismic process, we tested the used approach for two different 3-D models in which the dynamical features were changed from more regular to more randomised conditions by adding a certain degree of noise. An analysis of the variability in the extent of regularity of the seismic process was carried out for different completeness magnitude thresholds. The results of our analysis show that in about a third of all the 50-data windows the original seismic process was indistinguishable from a random process based on its features of temporal, spatial, and energetic variability. It was shown that prior to the occurrence of strong earthquakes, mostly in periods of generation of relatively small earthquakes, the percentage of windows in which the seismic process is indistinguishable from a random process increases (to 60 %–80 %). During periods of aftershock activity, the process of small earthquake generation became regular in all of the windows considered, and thus was markedly different from the randomised catalogues. In some periods within the catalogue, the seismic process appeared to be closer to randomness, while in other cases it became closer to a regular behaviour. More specifically, in periods of relatively decreased earthquake generation activity (with low energy release), the seismic process appears to be random, while during periods of occurrence of strong events, followed by series of aftershocks, significant deviation from randomness is shown, i.e. the extent of regularity markedly increases. The period for which such deviation from random behaviour lasts depends on the amount of seismic energy released by the strong earthquake.

Here we investigated a statistical feature of earthquake time distributions in the southern California earthquake catalog. As a main data analysis tool, we used a simple statistical approach based on the calculation of integral deviation times (IDT) from the time distribution of regular markers. The research objective is to define whether and when the process of earthquake time distribution approaches to randomness. Effectiveness of the IDT calculation method was tested on the set of simulated color noise data sets with the different extent of regularity, as well as for Poisson process data sets. Standard methods of complex data analysis have also been used, such as power spectrum regression, Lempel and Ziv complexity, and recurrence quantification analysis, as well as multiscale entropy calculations. After testing the IDT calculation method for simulated model data sets, we have analyzed the variation in the extent of regularity in the southern California earthquake catalog. Analysis was carried out for different periods and at different magnitude thresholds. It was found that the extent of the order in earthquake time distributions is fluctuating over the catalog. Particularly, we show that in most cases, the process of earthquake time distributions is less random in periods of strong earthquake occurrence compared to periods with relatively decreased local seismic activity. Also, we noticed that the strongest earthquakes occur in periods when IDT values increase.

The present analysis of research productivity of scholars in Georgia was motivated by the disadvantageous position of Georgia in international listings of the most cited scientific articles. We used official databases provided by governmental Shota Rustaveli National Scientific Foundation (SRNSF) from 2007 to 2013. In this research we have restricted our analysis by the consideration of bibliometric indicators of the leaders of the awarded projects. Three bibliometric characteristics: the number of publications and citations, as well as H-index of project leaders was obtained from SCOPUS database. According to our results, just 58% of all leaders of awarded projects in SRNSF grant competition, have an article (at least one) in the Scopus database for the entire period of their scholarly activity. From our analysis it follows that the quality of reviewing of the projects, presented to the SRNSF grant competition, does not promote a selection of the most productive project teams; there is no correlation between values of SRNSF reviewer's evaluation scores and the bibliometric data of project leaders in the Scopus database. As a result, in 2007–2012 in spite of large enough (for Georgia) funding, the problem of the low productivity and quality of scientific research in Georgia has not been resolved. We conclude that, in order to improve the situation with the low productivity of research in Georgia, the governmental programs of science support should be based on the new system of evaluation of the quality of presented projects; namely, peer-review approach should be combined with the bibliometric methodology. Besides local interest, for Georgian researchers and governmental authorities, the results of presented research have general importance in the light of ongoing international discussions about the necessity of inclusion of bibliometric data in evaluation procedures of research productivity. Presented results and discussions will be especially helpful for scholars and research administrators from countries in transition and could facilitate in elaboration of effective research funding policy.