Akademik Veri Yönetim Sistemi
QUATERNARY SCIENCE REVIEWS, cilt.23, sa.1-2, ss.161-174, 2004 (SCI-Expanded)
Electron spin resonance (ESR) ages were obtained on Al, E' and OH centres in quartz extracted from fault gouge from the North Anatolian Fault (NAF) in Turkey and the Nojima Fault (NF) in Japan. The data were used to test two contradictory criteria which have been used for the recognition of complete signal resetting during the fault movement: the grain-size plateau and the isochron models. The grain-size plateau method predicts decreasing ages with decreasing gain sizes because the fine grains are more intensely stressed during the faulting process. For those grains that were completely reset, a plateau of constant age is obtained and ESR ages derived from centres with different stress sensitivity converge. The isochron method is based on the fact that newly formed fracture surfaces are exposed to external alpha and beta radiation; thus, smaller grains ought to accumulate larger dose values. The plot of grain size versus external dose rate yields an isochron which gives the age of the fracturing process. It was found that most samples yielded smaller doses with decreasing grain sizes, thus, confirming the underlying principles of the grain size plateau method. However, only one sample yielded an extended plateau over a wider particle size range and converging ages for the different centres. The E' centre of the sample from the NF yielded the only result that indicated that the isochron method might work. The results derived from the E' centre of the other samples may have been interferred with by the so-called counterfeit E' signal, which may render those results unreliable.