HAKKODA, Northeast Japan

(40o39'22"N, 140o52'51"E)

(July 17, 97)
Carbon isotopic ratios, 13C/12C, of samples collected from the depression in question and springs nearby were determined by the Kusatsu-Shirane Volcano Observatory (KSVO).
Delta 13-C values are -5.7 per mil for CO2 in the gas collected from the depression floor on 13 July, -6.1 per mil for CO2 dissolved in water samples from the Hakkoda hotsprings (lemonade and alkaline springs), and -6.0 per mil for that in springwater from near the depression. The latter gas samles were collected on 14 July.

Commonly, delta 13-C of CO2 in volcanic gas in Japan ranges from -10 to 0 per mil, whereas that in CO2 gas of the organic origin from -30 to -20 per mil. The present data suggest the volcanic origin of the CO2-rich gas which killed three members of GSDF.

Information contacts: Takeshi Ohba and Jun-ichi Hirabayashi, KSVO, Tokyo Institute of Technology, e-mail: ohba@ksvo.titech.ac.jp, jhirabay@ksvo.titech.ac.jp, and VRC-ERI, U-Tokyo, e-mail: nakada@eri.u-tokyo.ac.jp.

(July 14, 1997)
Press (Asahi, Yomiuri, and Sankei) released the news that a party of the Ground Self Defense Force (Japanese army) accidentally inhaling gas was carried to emergency hospitals on the evening of 12 July, and three of them lost their lives until the 13 July noon. They were on a training mission at the northern foot of Hakkoda Volcano without gas mask. Some members slipped down into a depression (18 m long, 11 m wide, and 8 m deep) in the darkness, and collapsed on the bottom. His party rescuing them got frozen too. There were no plants within the depression, and leaves around it were dead. The fire station of the Aomori Prefecture mentioned that many holes and depressions emitting sulfurous acid gas locate around this volcano. Farmers interviewed spoke that several times they had witnessed dead animals in the depression.

According to Prof. J. Hirabayashi, Kusatsu-Shirane Volcano Observatory (KSVO), Tokyo Institute of Technology, who inspected the depression geochemically on 13 July, the gas collected from there contained CO2 as much as 15-20% in volume (much higher than the normal value of 0.035%), and no hydrogen sulfide was detected. He pointed out this accident probably due to high concentration of CO2 rather than sulfuric gas (H2S or SO2), and continued that the CO2 is either the volcanic origin or the organic matter origin. He intends to analyze the gas samples isotopically.

Hakkoda Volcano is ca. 20 km southeast of Aomori City (ca. 20 km north of Towada Volcano), consisting of stratocones and lava domes. The highest peak is Ootake (1,585 m). After the formation of the Minami (southern)-Hakkoda volcanic group (basalt, 3.9-0.5 Ma), the Hakkoda caldera was created due to a large-scale pyroclastic flow eruption (dacite, 1-0.8 Ma); followed by the formation of the Kita (northern)-Hakkoda volcano group (mainly andesite, 1-0.3 Ma) (Muraoka et al., 1985). There are strong solfataras around Ootake. There is no record of historic eruption.

Information contact: Jun-ichi Hirabayashi, KSVO, Tokyo Institute of Technology, e-mail: jhirabay@ksvo.titech.ac.jp, and Volcano Research Center, ERI, U-Tokyo, e-mail: nakada@eri.u-tokyo.ac.jp.

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