| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1998: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
1. This study clarified daily changes of amount of historical information in Rikkokushi, which are the most important chronicles describing the Japanese history from the Asuka period to the early Heian period (mainly during A.D.672-887). The number of Kanji characters of descriptions, which record phenomena and events day by day, were counted and regarded as a parameter for the amount of historical information. Although both the total information and the information about natural phenomena show similar tendency of increase with time, their amounts varies coincidently with changes of chronicle editors. Particularly, drastic increase of earthquake records at the chronicle boundary in A.D.850 suggests the change of editing policy of the chronicles. Thus, changes in earthquake frequency, which were calculated from the chronicle records, probably do not reflect the real seismicity in this period.
2. This study also clarified monthly changes of the number of historical diaries, which were written by government officials or priests in and around Kyoto during A.D.887-1595. In this period, the decrease of historical information in A.D.887, which was caused by the end of the Rikkokushi, is the most drastic change.
3. On the basis of the above results, this study reevaluated previous correlations between geological and historical records and pointed out their problems, which are of the A.D.878 Isehara earthquake, 762 Hida-Mino-Shinano earthquake, and 1331 Fuji earthquake. This study also pointed out the problems of commonly accepted views of changes in seismicity/volcanic activity, e.g. a seismicity peak in the 9th century in Japan, and a dormancy of Fuji Volcano during the 12-15th centuries.
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