Monitoring 222 Rn in soil gas of Garfagnana (Tuscany) aimed at earthquake prediction

Abstract

222 Rn concentration in soil gas from nineteen stations of Garfagnana valley (Central ltaly) was continuously monitored from December 1990 to May 1993. 222 Rn activity was measured by solid state nuclear track detector (SSNTD). Tracks detected by spark-counter and by optical microscope were proportionally constant for track densities lower than 2500 tracks/cm2. Since time variations in track density both for the same monitoring station and for different stations are significanfly higher than fluctuations in the experimental conditions, the validity of spark-counter for radon activity measurements is confirmed. Data collected in the period of monitoring indicate significant seasonal variations in radon concentration for every monitoring station. Moreover, the soil characteristics play an important role in determining the observed patterns. No significant correlation could be found between radon emission and seismicity. However, it should be noted that no earthquake with a magnitude higher than 3.5 occurred in Garfagnana during the monitoring period.