Radiological risk estimation from the terrestrial gamma dose rate in the seismically active Kopili Fault Zone, India

Abstract

ABSTRACT Anomalies in terrestrial gamma radiation have been reported in regions of seismic activity. The Kopili Fault in India is well-known for being extremely seismically active. Several mild to moderate-magnitude earthquakes with epicentres along the Kopili Fault Zone have recently been recorded. This necessitates a measurement of variations in gamma radiation and its associated radiological risks to the population in the region in relation to seismic activities. In this work, a portable gamma survey metre was used to measure terrestrial gamma radiations in the earthquake-prone Dhekiajuli area of Sonitpur district, India, which is located in the Kopili Fault Zone. Indoor and outdoor gamma dose rates were found to be 99.4 ± 5.1–195.9 ± 5.1 nGy h−1 (geometric mean: 159.0 ± 8.8 nGy h−1) and 99.4 ± 5.1–198.8 ± 5.1 nGy h−1 (geometric mean: 132 ± 6.5 nGy h−1), respectively. The estimated total annual effective dose equivalents (geometric mean: 0.94 ± 0.05 mSv y−1) were found to be higher than the recommended global average of 0.48 mSv y−1. The excess lifetime cancer risk was also estimated by considering the life span of an individual as 70 years, which ranged from 2.4 × 10−3 to 4.8 × 10−3.