INVESTIGATION OF CHANGES IN INDOOR RADON CONCENTRATIONS BEFORE AND AFTER SEISMIC ACTIVITIES IN GYEONGJU AND POHANG, KOREA

Abstract

This paper made a continuous measurement of the indoor radon concentrationsat a university building in Gyeongju, Rep. of Korea, to check if there is any notable pattern between the indoor radon concentrations and seismic activities. On September 12, 2016, earthquakeswith a magnitude of 5.1 and 5.8 consecutively occurred in Gyeongju. 14 months later, an earthquake with a magnitude of 5.5 occurred in Pohang, about 30 km away from Gyeongju, on November 15, 2017. This study investigated the change in the indoor radon concentrations before and after earthquakes to identify if there is any pattern between them and found an interesting pattern.Prior to earthquakes, radon anomalies, which are radon concentration deviating by more than ±2σ from the seasonal average, was usually identified. When 5.0 or greater magnitude earthquakes occurred, the indoor radon concentrations decreased sharply a few days before them, and then continuously increased until the occurrence of the earthquake.