Preseismic changes in atmospheric radon concentration and crustal strain

The anomalous increase in atmospheric radon concentration prior to the 1995 Kobe earthquake is compared with that in crustal strain and in other preseismic phenomena such as groundwater radon concentration, groundwater discharge rate and chloride ion concentration in groundwater. These preseismic phenomena are linked to fluctuations in crustal strain of the order of 10−6 to 10−8. The atmospheric radon concentration is the average or summation of radon released from a large area surrounding the monitoring station and the change can be quantitatively expressed by a power-law and log-oscillation model. These indicate that the observation of atmospheric radon is of benefit in the detection of the small anomalous preseismic crustal strain.