Stress Effect on Thermoluminescence Intensities of Quartz Grains　　―For the Establishment of a Fault Dating Method―

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概要

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• We have investigated the process of recovery of radiation damages at the time of fault movement, an elementary process attributed to stress, and examined the change of thermoluminescence (TL) intensities of quartz grains with diameters of 1-45 or 45-125 μ m , sheared under a slip rate of 100 μ m /s. 　　The following results were obtained as a result of the experiments. (1) TL intensities increase once with increasing stress, at larger rates for smaller grains. (2) With further increase in stress, the TL intensities peak then revert back to decrease, also at a larger rate for smaller grains. However, this reversion to original TL intensities occurs at higher stress for fine-grained samples. (3) Complete zeroing of TL intensities is not confirmed even at normal stress at ～60 MPa, regardless of grain size. 　　These observations have been interpreted as follows. (1) The increase of TL intensities with increasing stress is due to the so-called radiation damage increment induced by generation of detached electrons at the time of new surface formation caused by shear fracture. (2) The decrease of TL intensities is due to the recovery of damages at the stress where no substantial shear fracture occurs. (3) If a grain-surface phenomenon is responsible for both the increase and the decrease of TL intensities, then the effect is expected to be greater for finer grains, because the surface areas of samples with equal mass are inversely proportional to the radii. 　　The stress effect may not be the only factor contributing to the complete recovery of radiation damages at the time of fault movement. The possibility remains that a complete recovery may be brought about by a rise in temperature due to frictional heating. If the temperature rise were uniform throughout a crush zone, the effect should be independent of grain size, and the complete zeroing of TL intensities should depend only on the degree of temperature rise during fault movement. This is a subject for future studies, to establish a detection method of complete zeroing using the most appropriate TL method for evaluating the thermal hysteresis of samples.

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著者

• Hiraga Shozo

  Department of Earth Sciences, Nara University of Education

• Shimamoto Toshihiko

  Department of Geology & Mineralogy, Division of Earth & Planetary Sciences, Kyoto Universiy

• Hiraga Shozo

  Department Of Earth Sciences Nara University Of Education

• Shimamoto Toshihiko

  Department Of Geology & Mineralogy Division Of Earth & Planetary Sciences Kyoto Universiy

関連論文

• Stress Effect on Thermoluminescence Intensities of Quartz Grains　　―For the Establishment of a Fault Dating Method―
• How to Confirm “Complete Zeroing” in TL Dating of Fault Movement －Case of the Higashiura Fault，Awaji Island in Japan－

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