The reliability of earthquake predictions with radon in soil gas anomalies as precursors

The mechanical processes of earthquake preparation are always accompanied by deformations of elastic medium and the complex short- or long-term precursory phenomena can appear. In the scientific literature, there are many dozens precursors but none of them is reliable for earthquake prediction (in the sense of forecasting of time, place and magnitude of a forthcoming earthquake). The observed anomalies of radon concentrations in soil gas as well as in ground water before some earthquakes in Asia in late 60`s have triggered extensive and systematic investigations on the possibility to use radon as a reliable earthquake precursor. Radon concentrations in soil gas in Croatia were continuously measured since 1998 by the LR-115 nuclear track detectors [1] as well as by the Barasol semiconductor detector since 2005. The influence of the meteorological parameters on the temporal radon variations is investigated and the reduction (deconvolution) of the radon variation caused by the barometric pressure, rainfall and temperature is described [2]. The obtained “clear” radon time series signal is correlated to selected seismic events occurred in the vicinity of radon monitoring station. The calculated values of parameters in empirical equations between earthquake magnitude, epicentral distance and precursor time enable the determination of probability for a forthcoming earthquake that will occur at the epicentral distance R from the monitoring site in some expecting precursor time T [3, 4]. The reliability of these “earthquake predictions” (a posteriori) is discussed. [1] Planinic, Josip ; Radolic, Vanja ; Culo, Dominika. Searching for an earthquake precursor: Temporal variations of radon in soil and water. // Fizika A (Zagreb) 9(2) (2000) 75-82. [2] Planinic, Josip ; Radolic, Vanja ; Lazanin, Željko. Temporal variations of radon in soil related to earthquakes. // Applied Radiation and Isotopes, 55 (2001) 267-272. [3] Planinic, Josip ; Radolic, Vanja ; Vukovic, Branko. Radon as an earthquake precursor. // Nuclear Instruments & Methods in Physics Reasearch A, 530 (2004) 568-574. [4] Miklavcic, Igor ; Radolic, Vanja ; Vukovic, Branko ; Poje, Marina ; Varga, Maja ; Stanic, Denis ; Planinic, Josip. Radon anomaly in soil gas as an earthquake precursor. // Applied Radiation and Isotopes, 66 (2008) 1459-1466.