Estimation of fracture porosity using radon as a tracer

In this paper, a quantitative method using the precursory radon decline as a tracer to estimate fracture porosity is presented with the help of a case study. In a fractured confined aquifer of limited recharge, the in-situ volatilization of dissolved radon could cause a decline of radon in groundwater precursory to an earthquake. Based on the mechanisms of in-situ radon volatilization and rock-dilatancy, a mathematical model has been developed to correlate the radon decline with fracture porosity and volumetric strain change in the aquifer rocks.