Influence of strong electromagnetic discharges on the dynamics of earthquakes time distribution in the Bishkek test area (Central Asia)

T. Chelidze, V. De Rubeis, T. Matcharashvili, P. Tosi


From 08/01/1983 to 28/03/1990, at the Bishkek ElectroMagnetic (EM) test site (Northern Tien Shan and Chu Valley
area, Central Asia), strong currents, up to 2.5 kA, were released at a 4.5 km long electrical (grounded) dipole.
This area is seismically active and a catalogue with about 14100 events from 1975 to 1996 has been analyzed. The
seismic catalogue was divided into three parts: 1975-1983 first part with no EM experiments, 1983-1990 second
part during EM experiments and 1988-1996 after experiments part. Qualitative and quantitative time series non- linear
analysis was applied to waiting times of earthquakes to the above three sub catalogue periods. The qualitative
approach includes visual inspection of reconstructed phase space, Iterated Function Systems (IFS) and Recurrence
Quantification Analysis (RQA). The quantitative approach followed correlation integral calculation of reconstructed
phase space of waiting time distribution, with noise reduction and surrogate testing methods. Moreover the Lempel-
Ziv algorithmic complexity measure (LZC) was calculated. General dynamics of earthquakes temporal distribution
around the test area, reveals properties of low dimensional non linearity. Strong EM discharges lead to the
increase in extent of regularity in earthquakes temporal distribution. After cessation of EM experiments the earthquakes
temporal distribution becomes much more random than before experiments. To avoid non valid conclusions
several tests were applied to our data set: differentiation of the time series was applied to check results not affected
by non stationarity; the surrogate data approach was followed to reject the hypothesis that dynamics belongs to the
colored noise type. Small earthquakes, below completeness threshold, were added to the analysis to check results


seismic regime;strong electrical discharges;non-linear dynamics

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X