HR: 1340h
AN: T13C-1369    [Abstracts]
TI: Character, Provenance, and Recurrence Intervals of Holocene Turbidites in the Kushiro Submarine Canyon, Eastern Hokkaido Forearc, Japan
AU: * Noda, A
EM: a.noda@aist.go.jp
AF: Institute of Geology and Geoinformation, Geological Survey of Japan/AIST, Central 7, 1-1-1, Higashi, Tsukuba, Iba 305-8567 Japan
AU: Tsujino, T
EM: t-tsujino@aist.go.jp
AF: Institute of Geology and Geoinformation, Geological Survey of Japan/AIST, Central 7, 1-1-1, Higashi, Tsukuba, Iba 305-8567 Japan
AU: Furukawa, R
EM: furukawa-r@aist.go.jp
AF: Institute of Geology and Geoinformation, Geological Survey of Japan/AIST, Central 7, 1-1-1, Higashi, Tsukuba, Iba 305-8567 Japan
AU: Yoshimoto, N
EM: yosi@es.sci.kumamoto-u.ac.jp
AF: Department of Earth Science, Faculty of Science, Kumamoto University, 2-39-1, Kurokami, kumamoto, kum 860-8555 Japan
AB: Eastern Hokkaido forearc, Japan, is located on the Pacific side of the country along the Kuril Trench where large earthquakes and tsunamis have frequently occurred. The earthquake history in this region during the last few centuries is known, based on the historical literature. In order to examine prehistoric earthquakes, geological approach, such as analysis of seismo-turbidites or tusnami deposits, are effective. Two gravity cores (GH03-1033 and GH03-1034) were collected from the bottom of the Kushiro Submarine Canyon, offshore of Kushiro, eastern Hokkaido forearc. The cores contain evidence of several turbidites. Sedimentological, geochemical, and micropaleontological data and high-resolution seismic data have been used to identify character, provenance, and recurrence intervals of the turbidites. Upstream ($<$ 1000 m of the water depth), the Kushiro Submarine Canyon is presumed not to be a pathway for turbidity currents during Holocene, because an accumulation of thick mud lies in the channel. Tephras of Ta-a (AD1739), Ko-c2 (AD1694), Ta-b (AD1667), and Us-b (AD1663) were identified, and used to define the recurrence ages of the turbidite depositions. The provenance of the turbidites in core GH03-1034 collected from the middle part of the canyon was inferred to be the northern slope of the canyon deeper than the shelf edge, on the basis of sand composition and benthic foraminiferal analysis. Strong seismic shocks would have caused repeated turbidity currents into the Kushiro Submarine Canyon. The determined turbidite recurrences (rate of 68 years) are similar to the historical (rate of 79.7 years) and estimated (rate of 77.4 years) recurrence intervals of the earthquakes along the Kuril Trench.
DE: 7221 Paleoseismology
DE: 7230 Seismicity and seismotectonics
DE: 3022 Marine sediments--processes and transport
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting