JpGU-AGU Joint Meeting 2017

Presentation information

[EJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS09] [EJ] tsunami deposit

Tue. May 23, 2017 10:45 AM - 12:15 PM 201A (International Conference Hall 2F)

convener:Tetsuya Shinozaki(Center for Research in Isotopes and Environmental Dynamics (CRiED), University of Tsukuba), Takashi Chiba(Institute of Seismology and Volcanology, Hokkaido University), Daisuke Ishimura(Department of Geography, Tokyo Metropolitan University), Kazuhisa Goto(International Research Institute of Disaster Science (IRIDeS),Tohoku University), Chairperson:Takashi Chiba(Institute of Seismology and Volcanology, Hokkaido University)

11:30 AM - 11:45 AM

[MIS09-09] Magnetic fabric evidence for rapid, characteristic changes in the dynamics of the 2011 Tohoku-oki tsunami

*Balazs Bradak1,2, Koichiro Tanigawa3, Masayuki Hyodo2,4, Yusuke Seto4 (1.Research fellow of Japan Society for the Promotion of Science (JSPS), 2.Research Center for Inland Seas, Kobe University, Nada, Kobe, 657-8501, Japan, 3.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Site C7 1-1-1 Higashi, Tsukuba 305-8567, Japan, 4.Department of Planetology, Kobe University, Nada, Kobe, 657-8501, Japan)

Keywords:magnetic fabric , tsunami dynamics, 2011 Tohoku-oki tsunami

Magnetic fabric (MF) and rock magnetic measurements were applied to sediments deposited by the 2011 Tohoku-oki tsunami to reveal the dynamics of the tsunami run-up and the character of the sedimentation along the Misawa coast, Aomori Prefecture, northern Japan. Two main types of sedimentary environment are described: a higher energy, tangential stress-dominated environment with imbrication and traction/rolling transportation and a calmer, post-peak wave environment ruled by gravitational stress.
Rapid characteristic changes in the tsunami dynamics are also described. The tsunami began with erosion of the pre-tsunami surface caused by rapidly increasing energy. Bedload features such as ripple stratification were developed by the repeated accelerations and decelerations of the tsunami wave during run-up. The arrival of the peak wave was indicated by high-density flow, “slurry-like” sediments. Following the peak wave, the decreasing energy was marked by a change in MF.