Complex dynamics of fault zone deformation under large dam at various time scales

In the paper, we analyzed almost 40 years' long time series of fault zone strain, which crosses the foundation of the Enguri high arc dam (West Caucasus). The time series of fault strain reflect summary effect of tectonic, environmental and man-made impact. Our original contribution to the geomechanics of geo-energy is the first application of complexity theory methods to the analysis of fault zone monitoring time series. This lead to understanding complicated dynamics of the fault zone deformation, which reflects a joint influence of regional tectonics, local man-made stresses and environmental factors. Namely, we used recurrence plots, recurrence quantification analysis, mutual information and singular spectrum analysis to reveal evolution of hidden temporal patterns in the history of fault zone deformation, which cannot be detected by standard statistical methods. Using these mathematical methods of data-handling, we singled out contributions long-, intermediate- and short-term factors on the temporal variation of fault zone deformation and suggest corresponding interpretation of temporal patterns in terms of poroelasticity. Analysis of nonlinear dynamics of fault zone deformation can be useful for assessment of different components of the fault strain, affecting dam safety.