Changes in Dynamics of Seismic Processes Around Enguri High Dam Reservoir Induced by Periodic Variation of Water Level
The importance of elucidating the effects of small periodic influences on the behavior of complex systems is well acknowledged. In the present research, a possible impact of regular water level variations in large reservoir as an example of small external influence (comparing to tectonic forces) on the dynamics of local seismic activity was investigated.
In general, large reservoirs located in the seismically active zones are often considered as a factor which quantitatively and qualitatively influences the earthquakes generation. It was many times reported that during impoundment or immediately after it (namely from several months to several years), both the number and the magnitude of earthquakes around reservoir significantly increased. These changes in earthquake generation are named the reservoir induced seismicity (RIS). After several years of regular seasonal load/upload of the reservoir, the seismicity essentially decreases down to the level when lesser earthquakes occur with lower magnitudes. To explain this decrease, the authors of the present paper recently proposed a model of phase synchronization of local seismic activity by the periodic variation of the water level – the reservoir-induced synchronization of seismicity (RISS).
Generally speaking, RISS presumes a kind of control of local seismic activity by synchronizing small external periodic influence and hence an increase of the order in dynamics of regional seismic activity. To reveal these changes in dynamics of phase-synchronized seismic activity around a large reservoir, field seismic and water level variation data were analyzed in the present work. Data sets of laboratory stick-slip acoustic emission, under a weak influence imposed as a model of natural seismicity influenced by periodic water level variation, also were analyzed.
The evidence is presented showing that an increase of the order in dynamics of daily occurrence, as well as temporal and energy distribution of earthquakes took place around Enguri high dam water reservoir (Western Georgia) during the periodic variation of the water level in the lake.
It is shown that when the water level variation in a reservoir is close to periodic, monthly frequency of earthquake occurrence reveals two maximums: in spring and autumn. There is a clear asymmetry in the seismic response, possibly due to load/unload response ratio (LURR) effect; the maximal release of seismic energy is during loading, i.e., in the spring.
KeywordsAcoustic Emission Phase Synchronization Recurrence Plot Seismic Process Water Level Variation
We acknowledge INTAS (#0748, 2002) for funding our experimental investigations.
- Chelidze, T., Lursmanashvili, O., ‘Electromagnetic and mechanical control of slip: laboratory experiments with slider system’, Nonlinear Processes in Geophysics, 20, 2003, 1–8.Google Scholar
- Goltz C, Fractal and chaotic properties of earthquakes, Springer, Berlin, 1998.Google Scholar
- Marwan, N, Wessel, N., Meyerfeldt, U., Schirdewan, A., Kurths, J., Recurrence-plot-basedmeasures of complexity and their application to heart rate variability data. Physical Review E, 66, 2002, 026702.1-026702.8.Google Scholar
- Marwan, M., Encounters with neighborhood, PhD Thesis, 2003.Google Scholar
- Peinke, J., Matcharashvili, T., Chelidze, T., Gogiashvili, J., Nawroth, A., Lursmanashvili, O., Javakhishvili, Z., ‘Influence of Periodic Variations in Water Level on Regional Seismic Activity Around a Large Reservoir: Field and Laboratory Model’, Physics of the Earth and Planetary Interiors, 156/1-2, 2006, 130–142.Google Scholar
- Pikovsky, A., Rosenblum, M.G., Kurth. J., Synchronization: Universal Concept in Nonlinear Science, Cambridge University Press, Cambridge, 2003.Google Scholar
- Simpson, D., Leith, W., Scholz, C. ‘Two types of reservoir-induced seismicity’, Bulletin of Seismological Society America, 78, 1988, 2025–2040.Google Scholar
- Smirnov, V.B., ‘Fractal properties of seismicity of Caucasus’, J. of Earthq. Prediction Res. 4, 1995, 31–45.Google Scholar
- Trifu, C.I. (ed)., The mechanism of induced seismicity, Special Volume, Pure & Applied Geophysics, 159, 2002.Google Scholar