@article{oai:kumadai.repo.nii.ac.jp:00029862,
 author = {Takarada, Shinji and 星住, 英夫 and Hoshizumi, Hideo and Miyagi, Isoji and Nishimura, Yuichi and 宮縁, 育夫 and Miyabuchi, Yasuo and Miura, Daisuke and Kawanabe, Yoshihisa and 宝田, 晋治 and 星住, 英夫 and Hoshizumi, Hideo and 宮城, 磯治 and 西村, 裕一 and 宮縁, 育夫 and Miyabuchi, Yasuo and 三浦, 大助 and 川辺, 禎久},
 issue = {5},
 journal = {火山},
 month = {Nov},
 note = {application/pdf, 論文(Article), Events of the March 31, 2000 phreatomagmatic eruption at Usu Volcano can be subdivided into two stages: (1)large-scale black plume stage having 6 major events from 13:07 to 15:28, and (2)relatively small-scale, black plume and jet-type plume stage having 5 major events from 15:28 to 17:07. The total thickness of the March 31 deposit are 100 cm at a site 90 m north from the vent, 9 cm at 550 m NNE from the vent, and 2.5 cm at 1,030 m NE from the vent. The March 31 deposit at the proximal site (90 m north) comprises 10-70 mm thick 20 layers, consisting of sandy coarse 11 layers and sandy to silty matrix-supported 9 layers. The 20 layers at the proximal site can be correlated with each eruption event observed from 13:07 to 17:25 on March 31. In the proximal deposit, essential white pumice ratio is high in the early stage (42%), then the ratio decreases toward the final stage (up to 21%). Essential pumice fragments are white and subrounded, and contain many 0.05-0.2 mm vesicles. The pumice is relatively poorly vesiculated. Grain-size distributions of all layers in the proximal deposit show bimodal distributions, with peals at -0.5φ to 1φ and  6.5φ to 7.5φ. Poorly-sorted muddy layers are observed in post April 1 deposits. These layers formed during repeated phreatic explosions associated with abundant mud-clast spattering. The proximal area data show that the discharged mass of the March 31 deposit was 2.2×10^8kg in total and 1.1×10^8kg in the proximal area to 8 mm isopach., https://www.jstage.jst.go.jp/article/kazan/47/5/47_KJ00001053120/_article/-char/ja/},
 pages = {645--661},
 title = {有珠火山2000年噴火の火口近傍堆積物},
 volume = {47},
 year = {2002},
 yomi = {ホシズミ, ヒデオ and ミヤブチ, ヤスオ and ホシズミ, ヒデオ and ミヤブチ, ヤスオ}
}