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[MIS11-P16] The generation of tsunami deposit resulting from the 7.3 ka Kikai Caldera eruption along the Ishizaki River of northern Miyazaki Plain, southern Kyushu, Japan
Keywords:7.3 ka Kikai Caldera eruption, tsunami, tsunami deposit, Koya pamice, K-Ah volcanic ash, Miyazaki Plain
(1) The 7.3ka tsunami deposit is 28cm in thickness and consists of medium to coarse sand grain. This layer shows the high flow regime bedform like an antidune. Its base has a clear erosional surface, and covers the estuary mud layer. Pumice is at the bottom of the sand layer to be compared to Koya pumice is, on the other hand on the top include wood fossils are numerous. Sand layer is covered in reworked sediment in the water of the K-Ah volcanic ash. Thus the 7.3 ka tsunami struck Miyazaki coast only once between falling stages of Koya pumice and K-Ah volcanic ash. This event can be contrasted to the first of the earthquake events of the Akahoya period (Naruo and Kobayashi, 2002).
(2) K-Ah volcanic ash layer is 44cm in thickness, and convolute lamination is observed over the layer. As the cause of liquefaction, the second earthquake events of the Akahoya period (Naruo and Kobayashi, 2002).
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