HR: 1340h
AN: T33B-0531    [Abstracts]
TI: Northward Movement of the Manazuru Micro-plate in the Izu Collision Zone, Central Japan, Revealed by Paleomagnetism
AU: * Kimura, H
EM: haruo@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Sato, H
EM: satow@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-0032 Japan
AB: The active arc-arc collision in the Izu collision zone has many unique tectonic features. In spite of the overall northwestward movement of the Philippine Sea plate, northeastern part of the Izu Peninsula has potential moving northward as suggested by GPS [Ishibashi and Itani, 2004]. In order to study the northward motion of the block, we examined geologic slip-rates of its block boundary. To reveal the slip rate of the western boundary, paleomagnetic measurements were carried out around the Tanna fault zone. The minimum value of strike-slip displacement by the drag deformation during the past about 0.6 million years is about 6.4-9.6 km. Because the offset on the fault during past 0.6 million years inferred from tectonic geomorphology is about 1 km [Kuno, 1936], the total strike-slip displacement is more than about 7.4-10.6 km. The strike-slip component of the slip rate of the fault is greater than about 12.3-17.6 mm/yr. The southern margin of block is the zone from the Higashi-Izu monogenetic volcanoes to the Izu-Oshima Island as a divergence boundary. Based on a relation between growth of thickness of dyke and intervals of dyke intrusion events. The obtained value of extension is less than 17-20 mm/yr [Koyama, 1993] in the zone of monogenic volcanoes and 21-35 mm/yr at the Izu-Oshima Volcano. These values are concordant with the value observed along the Tanna fault by paleomagnetism and tectonic geomorphology. Consequently, we conclude that the northeastern part of the Izu Peninsula is moving toward the north-northeast at a velocity of about 12-21 mm/yr.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 8175 Tectonics and landscape evolution
DE: 8199 General or miscellaneous
DE: 9320 Asia
DE: 9604 Cenozoic
SC: Tectonophysics [T]
MN: Fall Meeting 2005