Dendrochronological Research on a Relation Between the Trees from the Botton of the Ashinoko Lake and the Great

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We took 17 samples from the Ashinoko Lake in 1997,1998. As they lost their sapwoods, we couldn't measure their accurate dates of the death of the trees. The result of the chronology consisted of 2 groups; one was about 500 AD., the other was 1000 AD. Estimating the tree rings of the lost sapwoods, the seasoned date of the former group was about 600 AD., the latter one was in about 1100 AD.. According to the old records, the great earthquakes occurred in 599 and 1096. We had a conclusion that the big trees grown on the steep slope were moved into the bottom of the Lake by landslide because of the earthquakes. Then such trees were sank into the bottom of the Lake. they look like inverted from the boat on the lake.Based on these researches , we think that the great earthquakes attacked this area had a cycle of about 500 years. And the result of the chronology using 14 C (about 350AD., and 900 AD.) was about 200 years earlier than using dendrochronology. We can crosscheck the reliability of the chronology using 14C. We believe that this research must be very helpful chronological information for predicting a future earthquake in this area.Now we are being involved in analyzing the tree rings of Chamaecyparis obtusa Endl. buried in the mud of Kamiyama Mt.. When this analysis is completed, we can clear the birth date of the Ashinoko Lake.