Abstract
The concentration of 222Rn in air in the gallery at Mikawa. Crustal Movement Observatory (Toyohashi City, central Japan) has been continuously measured with a flow-type ionization chamber since April, 1977 for the investigation of pre-earthquake anomalies. The observed 222Rn concentration shows remarkable increase after rainfall. It seems that 222Rn rich air is squeezed in the gallery by the contractile force caused by rainfalls from faults with elevated 226Ra content. The variation of 222Rn concentration in the gallery has been calculated from the rainfall data from June, 1977 to December, 1979. Sometimes remarkable disagreements between the observed and calculated values of the 222Rn concentration are seen before and after the occurrence of nearby earthquakes. Such a disagreement might be a precursor of nearby earthquake. The concentration of 222Rn is also influenced by the changes in atomospheric pressure; it increases as the pressure drops and decreases as the pressure rises. Seasonal variations are recognized, too. Continuous observation of 222Rn has also been started in June, 1980 at Kikugawa Crustal Movement Observational Station (Shizuoka Prefecture, central Japan).
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Schedule a callMore From: Zisin (Journal of the Seismological Society of Japan. 2nd ser.)
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