A study of soil radon and seismicity along active fault region in northeastern India

This paper reports the analysis of soil radon data collected from March 2013 to July 2016. LR-115 Type II solid-state nuclear track detectors were deployed to determine the concentration of radon in the soil at a depth of 80 cm. The data on soil radon were collected using the integrated measurement technique over a 7-day period. Soil radon is affected by environmental parameters in addition to geophysical phenomena. To study the effect of the environmental parameters on the measured radon data, we have performed the analysis of soil radon with the environmental parameters using the ARIMA model. We have used the ARIMA (2,0,2) model to calculate the predicted value of soil radon. The predicted value of radon obtained from the model was primarily due to variations in environmental parameters. Therefore, we calculate the difference (residual) between the actual and predicted values of radon and correlate it with the seismic events that occurred around the investigation area. An anomalous variation in the residual radon was recorded a few days prior to the M5.4 earthquake, which occurred at a distance of 123.9 km from the study area.