Japan Geoscience Union Meeting 2015

Presentation information


Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS28] Active faults and paleoseismology

Wed. May 27, 2015 4:15 PM - 6:00 PM 103 (1F)

Convener:*Takashi AZUMA(National Institute of Advanced Industrial Science and Technology), Nobuhiko Sugito(Faculty of Humanity and Environment, Hosei University), Satoshi Tonai(Department of Applied Science, Faculty of Scienece, Kochi University), Toshikazu Yoshioka(Active Fault and Earthquake Research Center, National Institute of Advanced Industrial Science and Technology), Chair:Takashi AZUMA(National Institute of Advanced Industrial Science and Technology)

4:45 PM - 5:00 PM

[SSS28-03] Late Holocene uplifts of Shikine Island on the northern Zenisu Ridge off Central Japan

*Takafumi IMAI1, Akihisa KITAMURA2, Mami ITO1, Yosuke MIYAIRI3, Yusuke YOKOYAMA3, Toshiyuki YAMAGUCHI4, Kaoru SUGIHARA5, Masataka ANDO6, Yuta MITSUI2, Haeng yoong KIM7, Mamoru NAKAMURA8 (1.Institute of Geosciences, Shizuoka University, 2.Faculty of Science, Shizuoka University, 3.Atmosphere and Ocean Research Institute, University of Tokyo, 4.Faculty of Science, Kanagawa University, 5.Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, 6.Center for Integrated Research and Education of Natural hazards, Shizuoka University, 7.Hot Springs Research Institute of Kanagawa Prefecture, 8.Faculty of Science, Ryukyu University)

Keywords:Shikine Island, Emerged marine sessile assemblages, Late Holocene, uplifts, ^{14}C dating

Emerged marine sessile assemblages are observed on Shikine Island, located on the northern Zenisu Ridge in the northern Philippine Sea plate, Japan. A previous study obtained 14C ages of 1400 years BP from these assemblages by the liquid scintillation counter method and concluded that approximately 3 m of uplift occurred suddenly at 1400 years BP (Ota et al., 1983). The present study examined emerged assemblages at four sites on the island, and dated the assemblages at all four sites, and well as the assemblages reported by Ota et al. (1983), by accelerator mass spectrometry (AMS) 14C dating. The results show that all the specimens are younger than AD 950. The difference in ages between the previous work and this study reflects contamination by dead carbon of the specimens measured in the previous work. By combining the our 14C age data of the emerged sessile assemblages and faunal analysis of present-day rocky intertidal sessile assemblages around the study area, we suggest that uplift events took place at AD 1120-1400, AD 1530-1890, and AD 1858-1950. The amount of uplifts were estimated to be 0.4-1.8 m. It is likely that the modern uplift was due to an earthquake which occurred along south Zenisu fault system at AD 1890. The two older uplift events were caused by either fault motion or igneous activity. Although the timing of the uplift event at AD 1530-1890 corresponds to AD 1605 Keicho earthquake, our fault model did not support relationship between the uplift event and the earthquake. In conclusion, this study do not support possibility that tsunami source areas of AD 1498 Meio and 1605 Keicho tsunamis were located at the northern Zenisu Ridge.