Concentration of radon

Various studies and observations have indicated an increase in radon concentration in the run-up to a quake. However, such an increase is not a reliable predictor because an elevated radon concentration can only be associated with seismic activity in around 10% of cases. Furthermore, the distance between the radon measurement and the epicentre (up to 1,000 km away), the time periods in question (ranging from hours to months) and the measured magnitudes differ widely, and so far no reliable correlation between the individual parameters could be found.