Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

S (Solid Earth Sciences) » S-VC Volcanology

[S-VC41] Active Volcanism

Wed. May 23, 2018 3:30 PM - 5:00 PM International Conference Room (IC) (2F International Conference Hall, Makuhari Messe)

convener:Yuta Maeda(Nagoya University), Takahiro Miwa(National research institute for earth science and disaster prevention), Yosuke Aoki(東京大学地震研究所, 共同), Takeshi Nishimura(Department of Geophysics, Graduate School of Science, Tohoku University), Takahiro Ohkura(Aso Volcanological Laboratory, Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Satoshi Okumura(Division of Earth and Planetary Materials Science, Department of Earth Science, Graduate School of Science, Tohoku University), Tomofumi Kozono(Department of Geophysics, Graduate School of Science, Tohoku University), Chairperson:Suzuki Takehiko, Miwa Takahiro

4:15 PM - 4:30 PM

[SVC41-52] Integrated marine investigations of Kikai Caldera, SW Japan

*Tetsuo Matsuno1,2, Yoshiyuki Tatsumi1,2, Nobukazu Seama2,1, Keiko Suzuki-Kamata1,2, Hiroshi Ichihara3,1, Koji Kiyosugi4,1, Reina Nakaoka1, Satoshi Shimizu1, Mamoru Sano1, Hikaru Iwamaru1, Haruhisa Morozumi1, Hiroko Sugioka2,1, Kazuo Nakahigashi5,1, Yojiro Yamamoto6, Kazuki Hayashi2, Kimihiro Nishimura2, Yuka Furukawa2, Misaki Horiuchi2, Daichi Nakata7, Ryoto Nakamura7, Hirose Toki8, Yasutomo Seto8, Atsuhiro Oshige9, Hideaki Takizawa10, Tatsuro Chiba11, Shuichi Kodaira6 (1.Kobe Ocean Bottom Exploration Center, Kobe University, 2.Department of Planetology, Graduate School of Science, Kobe University, 3.Graduate school of environmental studies, Nagoya University, 4.Organization of Advanced Science and Technology, Kobe University, 5.Tokyo University of Marine Science and Technology, 6.Japan Agency for Marine-Earth Science and Technology, 7.Division of Marine Engineering, Graduate School of Maritime Sciences, Kobe University, 8.Department of Planetology, Faculty of Science, Kobe University, 9.Department of Marine Engineering, Faculty of Maritime Sciences, Kobe University, 10.Johnny & Associates, Inc, 11.Asia Air Survey Co., Ltd.)

We started integrated marine investigations of Kikai Caldera with T/S Fukae-maru of Kobe University on October, 2016. Aims of our investigations are to reveal the structure of the caldera, the existence of magma reservoir, and to understand the mechanism of catastrophic caldera-forming eruption at 7.3 ka and a potential for a future catastrophic eruption. We conducted multi-beam echo sounder mapping, multi-channel seismic reflection (MCS) surveys, remotely operated vehicle (ROV) observations, rock sampling by dredging and diving, geophysical sub-seafloor imaging with ocean bottom seismometers, electro-magnetometers (OBEMs), some of which equip absolute pressure gauge, ocean-bottom magnetometers, and surface geomagnetic surveys.

The first finding of our investigations is lines of evidence for creation of a giant rhyolite lava dome (~32 km3) after the caldera collapse. This dome is still active as water column anomalies accompanied by bubbling from its surface are observed by the water column mapping. Chemical characteristics of dome-forming rhyolites akin to those of presently active small volcanic cones are different from those of supereruption. The voluminous post-caldera activity is thus not caused simply by squeezing the remnant of syn-caldera magma but may tap a magma system that has evolved both chemically and physically since the 7.3-ka supereruption.

We have been conducting integrated analyses of our data set, and have planned the fourth research cruise with T/S Fukae-maru on March, 2018, consisting of MCS survey, ROV observation, OBEM with absolute pressure gauge observation, and bathymetric and surface geomagnetic survey. We will introduce results of the data analyses and the upcoming cruise in the presentation.