Radon transport in the earth: a tool for uranium exploration and earthquake prediction

The 222Rn concentration in the ground near the surface of the earth provides a sensitive signal for recognizing subterrestrial flow of fluids. Such flows can indicate the existence of regions of enriched 222Rn and hence the presence of subsurface uranium ore. If such flows are caused by stress buildup prior to earthquakes, they can give premonitory signals. Systematic variations in near-surface radon have been observed near ore deposits and in earthquake zones, and are ascribed to subterrestrial flow of fluids. Changes in radon concentration have been seen that are not ascribable to earthquake-related effects. Temperature, pressure, moisture, and prevailing winds have been considered but do not correlate with the radon changes. Earth tidal triggering of these events is the only known possibility that presently cannot be ruled out; it is being assessed. Earthquake related changes in radon concentration have been measured at considerable distances from the hypocenters of earthquakes. A simple dislocation model leads to estimates of distance that increase to hundreds of kilometers at earthquake magnitudes of five and above. (author)