Temporal variation of soil radon and thoron concentrations in Mizoram (India), associated with earthquakes

Continuous soil-gas radon and thoron measurements were carried out at 15 days interval along Mat fault in Mizoram (India), which lies in the seismic zone V of the seismic zonation map of India. The study was carried out from March 2012 to February 2013 using LR-115 Type II detectors, manufactured by Kodak Pathe, France. The effect of meteorological parameters on radon and thoron data was taken into consideration. The annual average value of radon and thoron concentration was found to be 621.21 and 590.18 Bq/m<Superscript>3</Superscript> with a standard deviation of 377.60 and 301.34 Bq/m<Superscript>3</Superscript>, respectively. Inverse correlation coefficient was obtained between radon/thoron concentration and the meteorological parameters except in one case (thoron and relative humidity) which showed a weak positive correlation. Standard deviation method was employed in order to differentiate those anomalies which are solely caused by seismic events and not by meteorological parameters. The data obtained have been correlated with the seismic activities that occurred around the measuring site. Positive correlations were found between radon/thoron data and the earthquakes. Copyright Springer Science+Business Media Dordrecht 2014