Preseismic Atmospheric Radon Anomaly Associated with 2018 Northern Osaka Earthquake (IMAGE) Tohoku University Caption Image showing the exhalation of radon (222Rn) gas from underground. The concentration of radon in the atmosphere is measured at radioisotope (RI) facilities. Radon exhalates to the ground surface through microcracks (fissures) in the rock that occur before and after earthquakes. Credit Jun Muto Usage Restrictions Jun Muto License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.