RADON MONITORING WITH PLASTIC DETECTORS IN EARTHQUAKE PREDICTION

Since 1984 a German-Turkish co-operation on earthquake prediction has existed at the North Anatolian fault zone in Turkey. Besides investigations on other parameters, changes in radon concentration are observed. The cellulose nitrate "Kodak LR115 Type II pelliculable" from Kodak-Pathe, France, and the 300-mu-m thick allyl diglycol carbonate CR-39 from Pershore Mouldings, U.K., are used in recording alpha-particles from radon and its daughter isotopes. The etching behaviour of both detectors has been measured. For LR115 an etchant-creeping effect at the boundary layer between the 13.5-mu-m CB-detector and the supporting 99.5-mu-m polyester base was observed. Based on these results a theoretical calculation of the so-called "sensitive volumes" was carried out. The most important result was the calculation of the Rn-sensitivities for both detectors. The calculated LR115/CR-39 sensitivity ratio was found to be equal to the measured track density ratioS D(CR-39)/D(LR115) = 2.14 +/- 0.81. Moreover, we found that the etching behaviour of LR115 is different from that of "Kodak CA 80-15"; this was formerly believed to be the same because the same raw cellulose nitrate material was involved in both cases.