ELECTRIC FIELD AT «KARYMSHINA» STATION IN AUGUST 2009 AND THEIR RELATIONS TO THE INCREASE OF GLOBAL SEISMICITY

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Potential gradient of the atmospheric electric field was measured simultaneously at the height of 7 cm and
3.6 m above the surface in July - October 2009 at the Karymshina station (Kamchatka). In fair weather at
night and in the morning (local time) on August 8, 12, and 14 we registered the cases of reduction of potential
gradient only at the height of 7 cm with the further decrease to the previous level. Their minimum values were
negative. Such local anomalies were not observed any more in fair weather conditions. Negative anomalies of
electric field were registered at a certain height prior to earthquakes in various seismically active zones of the
world (Rulenko, 2000, a review). The occurrence of this anomalies near the surface and the lack of those at
higher altitudes were registered for the first time. The global-regional model of preparation of strong earth-
quakes (Shirokov, 2001, 2009) suggested that the final preparation stage is related to a short-term (lasting for
a few days) global rearrangement of the tectonic stress field. As a result, operative precursors are observed in
geophysical fields located at any distance from the source of a preparing earthquake. From August 9 to 17,
2009 there was an increase in global seismicity when 6 M ≥ 6.6 earthquakes occurred within 7.5 days. Whereas
on August 10 Indonesia suffered a М = 7.5 earthquake while no earthquakes М ≥ 5.0 occurred from August 1
to 20 in the Kurile-Kamchatka subduction zone. Since the negative anomalies of the electric field coincide in
time with the increase in global seismicity, we may consider them as a remote short-time precursors to a М =
7.5 earthquake. In the meantime, such an earthquake is supposed to indicate the rearrangement of the global
seismotectonic stress field.