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M9 Tohoku Earthquake Hydro- and Seismic Response in the Caucasus and North Turkey

Chelidze T. L., Shengeli I., Zhukova N., Matcharashvili T., Melikadze G., Kobzev G.

Acta Geophysica

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2016

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Vol. 64, no. 3

567--588

EN

Presently, there are a lot of observations on the significant impact of strong remote earthquakes on underground water and local seismicity. Teleseismic wave trains of strong earthquakes give rise to several hydraulic effects in boreholes, namely permanent water level changes and water level oscillations, which closely mimic the seismograms (hydroseismograms). Clear identical anomalies in the deep borehole water levels have been observed on a large part of the territory of Georgia during passing of the S and Love–Rayleigh teleseismic waves (including also multiple surface Rayleigh waves) of the 2011 Tohoku M9 earthquake. The analysis carried out in order to find dynamically triggered events (non-volcanic tremors) of the Tohoku earthquake by the accepted methodology has not revealed a clear tremor signature in the test area: the Caucasus and North Turkey. The possible mechanisms of some seismic signals of unknown origin observed during passage of teleseismic waves of Tohoku earthquake are discussed.

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Discrimination between stochastic dynamics patterns of ambient noises (Case study for Oni seismic station)

Matcharashvili T., Chelidze T., Javakhishvili Z., Zhukova N., Jorjiashvili N., Shengelia I.

Acta Geophysica

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2013

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Vol. 61, no. 6

1659--1676

EN

Investigation of complex dynamics of ambient seismic noise remains as an important scientific research challenge. In this work we investigated dynamical features of the ambient noises at Oni seismic station, Georgia. We used stochastic model reconstruction method from measured data sets. Seismic records for different time periods around Oni seismic station have been analysed. It was shown that the dynamics of fluctuations of seismic noise vertical component undergoes essential changes for considered time period from 2005 to 2012. These changes are more noticeable for time periods of preparation and aftershock activity of strong M6.0 earthquake occurred in 2009 in the vicinity of Oni seismic station.

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Scaling features of ambient noise at different levels of local seismic activity. A case study for the Oni seismic station

Matcharashvili T., Chelidze T., Javakhishvili Z., Zhukova N.

Acta Geophysica

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2012

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Vol. 60, no. 3

809-832

EN

Investigation of dynamical features of ambient seismic noise is one of the important scientific and practical research challenges. We investigated scaling features of the ambient noises at the Oni seismic station, Georgia, using detrended fluctuation analysis method. Data from this seismic station, located in the epicentral zone of Oni M6.0, 2009, earthquake, were selected to include time periods with different levels of local seismic activity. It was shown that the investigated ambient noise is persistent longrange correlated at calm seismic conditions in the absence of earthquakes. Fluctuation features of the analyzed ambient noises were affected by local earthquakes, while remote seismic activity caused just slight quantitative changes. Processes related to the preparation of a strong local earthquake may cause quantifiable changes in fluctuation features of ambient noises. Fluctuation features of seismic noise for periods of increased local seismic activity cease to be long-range correlated and appear to become a complicated mixture of random and correlated behaviours.