The Distribution of Radon Concentration in Caves

Radon concentration in caves is known to vary within an extremely wide range. Here the distribution of the average values of radon concentration is examined and a power law describing is identified, i.e. radon concentration has a fractal dimension D=1.26. This fact means that concentrations are not grouped around a mean value, a characteristic common to many other phenomena. Introduction Radon concentration in caves was measured all over the world since some decades, and a fairly large amount of data is available. The causes of variation of radon concentration are many and, often, cannot be easily identified. In addition to the source of radon, i.e. the concentration of uranium and radium in the rock in the vicinity of the cave, earth tide, atmospheric pressure, water flow, earthquakes, etc. influence the release and distribution of radon in the cave atmosphere. It must be emphasised that such a large number of factors is the reason why the measurement of radon concentration cannot be practically used for earthquakes forecasting, as it was thought in the past. In other words, it is possible to link the change of radon concentration to an earthquake but only after it occurred and not in advance, as it would be necessary for warning reasons. In nature many systems display self-organised criticality. The well known Gutenberg-Richter law concerning the distribution of earthquakes correlates the frequency against the magnitude by a power law with -2 exponent; such a law was recently also generalised (Kossbokov & Nekrasova, 2003). Other experiments carried out on the distribution of fragments resulted in a power law with -2.6 exponent (Oddershede et al., 1993). Many experiments found that a power law describes frequently a rather large number of distributions in very different fields (Turcotte, 1992). Int. J. Speleol., 32 (1/4) 2003: 113 115 1 Frazione Tuffo, I-14023 Cocconato (Asti), Italy e-mail:[email protected] n. 32 18-07-2004 20:24 Pagina 113