著者

小室 裕明

出版者

地学団体研究会

雑誌

地球科學 (ISSN:03666611)

巻号頁・発行日

vol.40, no.2, pp.115-123, 1986-03-25

被引用文献数

1

---

本宿型陥没構造(cauldron)は,1.ドーム隆起,2.陥没形成,3.噴火,という形成過程をふみ,いくつかの陥没が討究する傾向がある.隣接する陥没盆地間の中心距離は,数km〜30km,平均して20km程度である.このように陥没盆地がある一定の距離を隔てて等間隔配列をするのは,それぞれの盆地に対応してマグマ溜りが深部の低密度の部分溶融層から浮上してきたためと考えられる. Rambergによる重力不安定の理論式にもとずいて,20kmの卓越波長を生じる条件を数値計算した.モデルは2層構造であり,上層/下層(浮上層)の比が,0.2, 0.5, 1.0, 2.0, 5.0, 10.0の6通りのケースを設定して,粘性係数比と肩摩の関係を求めた.その結果,卓越波長は,上層の厚さ(部分溶融層の深さ)にはほとんど無関係であり,部分溶融層の厚さに大きく影響される.20kmの卓越波長を与える溶融層の厚さは6km以下である必要がある.

著者

岡本 泰子 小室 裕明

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.115, no.12, pp.635-642, 2009 (Released:2010-05-29)

参考文献数

28

---

縦長型マグマだまりの膨張ないし収縮によって形成されるカルデラを,アナログ実験で再現した.アナログ地殻は上新粉(米の粉末),アナログマグマだまりはゴム風船を使用した.実験結果は以下の通り.1.マグマだまりの膨張によってドーム隆起が生じ,ドーム頂部にグラーベン状に小さな漏斗型陥没が形成される.陥没の直径は,実際のスケールでは0.8~1.6 kmなので,カルデラというにはやや小さい.2.マグマだまりの収縮によって,平坦な底を持つ浅いカルデラと,その中心部の小径陥没が形成される.実際のスケールでは,カルデラの大きさは0.9~4.4 km,深さ200~400 mとなる.このモデルは,キラウエアカルデラと相似である.3.膨張後に収縮するマグマだまりによって形成されるカルデラは,先行するドーム隆起による地殻ダイラタンシーのため,マグマだまりが収縮するだけのモデルに比べて陥没量が小さくなる.

著者

小室 裕明 志知 竜一 舌間 洋二

出版者

島根大学

雑誌

島根大学地球資源環境学研究報告 (ISSN:13439774)

巻号頁・発行日

vol.19, pp.97-100, 2000-12-25

---

A Bouguer gravity anomaly map of the Unzen volcanic area founded on 590 gravity stations suggests the following volcanic structures:1.The gravitational Unzen graben shows a linear north rim along the Chijiwa fault.However,the gravitational south rim does not coincide with the Futsu fault which is the topographical south rim of the Unzen graben.2.The source of a low gravity anomaly in Tachibana-wan Bay has been considered as mass deficiency of caldera origin,but it may in fact be due to the emplacement of a large magma body.

著者

小室 裕明 志知 龍一 和田 浩之 糸井 理樹

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.41, no.1, pp.1-10, 1996-03-05 (Released:2017-03-20)

参考文献数

31

---

Sanbe Volcano is a large lava dome, 2 km in diameter, emplaced at the center of an elliptical caldera with a long axis of 7 km and a short axis of 5 km. One crater is exposed in the center of this dome, and four peaks surround this crater. However, the basement depth of the caldera has not been determined. We have made gravity measurements around Mt. Sanbe in order to investigate the caldera morphology. The residual gravity anomaly (which is obtained after the regional gravity trend is taken away from the Bouguer anomaly, assumed to be 2.67 g/cm3 in density) is low at the center of Sanbe Caldera. Mass deficiency, estimated by Gauss's theorem, indicates that Sanbe Caldera is one of the low anomaly type calderas, as large as the Mashu caldera. Basement depression under Sanbe Caldera has been determined by three dimensional analysis, when the density contrast between the basement rocks and Sanbe volcanic rocks is 0.43 g/cm3. The depression is square shaped, with a steep rim and a flat floor. The square outline suggests that the depression part may be subsided along normal faults ; accordingly this caldera may have originated in a cauldron. The western and eastern rims of the depression correspond to the somma, but the northern and southern rims are discordant. The poor topographic expression in these areas may be due to collapse of the caldera walls. The deepest part of the basement is centered on the east side of the present crater. This deep center may be the only vent of Sanbe Volcano, because other depressions are not observed beneath the lava dome.

著者

沢田 順弘 當銘 あかね 小林 伸治 小室 裕明 北川 博也 村上 久

出版者

The Geological Society of Japan

雑誌

地質學雜誌 (ISSN:00167630)

巻号頁・発行日

vol.105, no.4, pp.VII-VIII, 1999-04

被引用文献数

2 1

著者

小室 裕明

出版者

地学団体研究会

雑誌

地球科學 (ISSN:03666611)

巻号頁・発行日

vol.32, no.2, pp.68-82a, 1978-03-25

被引用文献数

2

---

The middle to the upper Miocene series in the Yanaizu region is divided into five formations, namaly the Ogino, the Urushikubo, the Shiotsubo, the Sunagohara, and the Fujitoge formations in ascending order, all of which are in conformable relation except that the unconformities at the base of the Sunagohara formation and partly at that of the Fujitoge formation. The Urushikubo formation may unconformably overlie the Ogino formation in part. The Ogino formation and the lower part of the Urushikubo formation consist of pyroclastic rocks. The upper part of the Urushikubo formation, the Shiotsubo formation, and the lower part of the Fujitoge formation consist of shale, sandstone, and siltstone respectively. The Sunagohara formation and the upper part of the Fujitoge formation consist of pyroclastic rocks. Basaltic, dacitic, and rhyolitic dykes intrude into the Urushikubo and the Shiotsubo formations. The fundamental geologic structure is nearly flat, except for some flexure, synclines and anticlines which have N-S trending axes. The horizontally bedded Sunagohara formation is distributed in a restricted area, about 5 km in diameter, and abuts on the steedly dipping surface of the unconformity at the margin of the basin. Basal conglomerate, which is very poorly sorted and angular talus-like breccia including boulder gravel with 3m in maximum diameter, is distributed along the margin. It would be deposited just in front of the abrupt cliff which has been preserved as the present steep surface of the unconformity. Normal faults striking parallel to the surface of the unconformity are found in the basement and by them such a cliff would formed. It is concluded that the collapse basin with 5 km in diameter was formed by the faulting which had thrown down the basin side abut 400 m before deposition of the Sunagohara formation. Before the formation of this collapse basin, the domal uplift which is 25 km in diameter and 500 m in height took place. Judging from that the collapse basin was filled with pyroclastic rocks which was deposited soon after the collapse, the domal uplift is ascribed to the magmatic activity. The other uplift with the axis of NW-SE trend, which was no relation to volcanism had took place in this region before the domal uplift.