RADON RECORDING OF UTTARKASHI EARTHQUAKE

Spatial and temporal distribution of radon is recorded in both soil-gas and groundwater using two different techniques, viz. track etch method and emanometry. Radon recording stations have been set up at one site in Amritsar and four sites in the Kangra valley (Himachal Pradesh) under the Himalayan seismicity project. The track-etch method gives integrated measurement of radon over a week or a fortnight whereas emanometry is used for daily recording of radon activity in soil-gas and groundwater. The Uttarkashi earthquake (m(b) = 6.5, M(S) = 7.0) occurred on October 20,1991 (Oct. 19 U.T.) in the Garhwal Himalayas (30.78-degrees-N, 78.77-degrees-E) about 330 km from our recording stations in the Kangra valley and about 450 km from Amritsar, respectively. Radon anomalies were recorded at all sites in Kangra valley and Amritsar about a week before the Uttarkashi earthquake, which clearly establishes that radon changes can be effective for forecasting some earthquakes.