2:15 PM - 2:30 PM
[HDS17-03] Oxygen isotopic dendrochronology of a gigantic rock avalanche and its comparison with historical documents -an interim report of the research group on high resolution chronology of large deep-seated landslides
Keywords:dendrochronology, oxygen isotope ratios, large landslide, Akaishi Range, Gokishichido earthquake
On the basis of radiocarbon age of 809-987 CalAD (2-sigma) measured for another tree trunk sample at the same outcrop (DDK-D: Kariya, 2012), four candidates of paleoseismic events can be listed in existing documents (e.g., Usami, et al., 2013, Materials for Comprehensive List of Destructive Earthquakes in Japan, 599-2012, Tokyo University Press), such as earthquakes at AD 841 in Shinano area, AD 841 Izu, AD 878 Kanto resion, and AD 887 Goki-Shichido, if it is assumed that the rock avalanche was induced by strong ground motion from a large earthquake. Oxygen isotopic dendrochronology age of DDK03 (AD 883+x), however, narrows the four candidates down to a single one of the AD 887 Goki-Shichido earthquake. This is consistent with Kariya et al. (2014; JPGU 2014, HDS29-P01); they performed conventional dendrochronology of the same DDK03 sample with the use of the fluctuation pattern of tree ring width and microscopic observation of cell structures of the outer most tree ring, and concluded that DDK03 died in the late summer of AD887 and that slope movement related to the rock avalanche might have been caused by the AD 887 Goki-Shichido earthquake.
This study was partly supported by the 2015 open grant of Japan Society of Erosion Control Engineering.