|Budget Amount *help
¥1,600,000 (Direct Cost : ¥1,600,000)
Fiscal Year 1992 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1991 : ¥1,100,000 (Direct Cost : ¥1,100,000)
At first, the accumulation rate of radiation charge of thermoluminescence in several conditions are studied in this research. As the results, accumulation of radiation charge weren't occur in the lead box of the thickness 10cm. The additional radiation charge in the brass or copper tubes did not occur. It is revealed that the radiation charge of the thermoluminescence elements laid under the ground were different at each region. So, it is clear that the radiation charge rate must be measured at the same point where tephra were sampled.
In San'in district, the author examined the tephra layers as to refractive index of volcanic glass, mineral composition and a so on. And as a reference, some samples of tephra distributed in Hokuriku district were examined. And also, the thermoluminescence intensity of these tephra were measured. It is revealed that this technique is able to apply for all of these tephra. However, the radiation charge accumulation is a very few in some tephra because of their mineral composition. For example, K-Tz, which contains large quantities of quartz particle, has large radiation charge accumulation. On the other hand, the tephra of Oginsen area, which are older than K-Tz as to stratigraphically, their thermoluminescence intensity are weak. And the thermoluminescence of the quite older pyroclastic flow deposits of Hokuriku is quite strong in comparison with the K-Tz. Daisen fallout pumices have a clear deference thermoluminescence intensity each other. The thermoluminescence intensity of tephra can be calculated into their fallout age.