Increase of radon and thoron volumetric activity at Kamchatka before the catastrophic earthquake in Japan on March 11, 2011

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   The paper presents the results of measurements of radon Rn and thoron Tn
   volumetric activity at Karymshina observation point (52.814⁰N,
   158.105⁰E) that is located in the area of Verkhnyaya-Paratunka
   hydrothermal system in Kamchatka. From December 27, 2010 to May 20, 2011
   the measurements were carried out in the 4-meter deep dry perforated
   borehole and at the height of 5 cm above the ground surface and 1 meter
   from the borehole pipe in a wooden cabin. Atmospheric pressure, air
   temperature and relative humidity in the cabin were measured by a climatic
   chamber of radiometer. From January 25 to February 11 large increases of
   Rn and Tn values relative to the background in the borehole were
   registered and from February 8 to 19 the Rn and Tn values increased near
   the borehole pipe. The increases of Rn and Tn values in the air occurred
   during the changes in atmospheric pressure of synoptic scale and had
   highly significant negative correlation with these changes. These
   variations of atmospheric pressure were absent during Rn and Tn
   disturbances in the borehole. There were no other Rn and Tn disturbances
   in the borehole and in the air near the borehole pipe within the period of
   measurements. Analysis of Ks >= 10.0 earthquakes occurred at the distance
   of 200 km from Karymshina observation point revealed that local seismicity
   did not increase during Rn and Tn disturbances. Rn and Tn disturbances in
   the borehole appeared 44.7 days before the earthquake on March 11, 2011 in
   Japan with magnitude of 9.0, the epicenter of which was 2000 km from
   Karymshina observation point. According to the data of Sobolev G.A. [Earth
   Physics, 2011. N 12. P. 11-22], Petropavlovsk seismic observatory, that is
   43 km from Karymshina observation point, recorded repeatedly the increase
   of intensity of low frequency seismic noise in a minute range of periods
   1.5 month (45 days) before this earthquake.

   So, we can assume that anomalous disturbances of radon and thoron
   volumetric activity in the borehole could be associated with the
   preparation of the catastrophic earthquake in Japan and the increases of
   their activity in the air near the borehole resulted from the decreases of
   the atmospheric pressure during cyclones.