著者

早川 由紀夫 萩原 佐知子 野村 正弘 小山 真人

出版者

日本地図学会

雑誌

地図 (ISSN:00094897)

巻号頁・発行日

vol.53, no.1, pp.57-65, 2015

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<p>We have intended to popularize geological maps, which are restricted professional uses presently. Two geologists, a map designer, and a print coordinator worked together to publish two maps at Asama Volcano and five maps in Izu Peninsula. They are easy to read for everyone because topographic relief is used as a base map. Every map was finished beautiful enough you want to exhibit it on the walls. We sell those maps not only at local shops but through the Internet for 500 yen, a surprisingly lower price than existing geological maps.</p>

著者

小山 真人

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.103, no.5, pp.576-590, 1994-10-25 (Released:2009-11-12)

参考文献数

56

被引用文献数

4 7

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Izu Peninsula and adjacent areas, which are located on the northern tip of the Izu-Bonin volcanic arc, are characterized by intense crustal movements and volcanic activity. Many geomorphological, geological, and geophysical data were collected from this area and various tectonic models were proposed to explain them systematically. These tectonic models can be classified into two categories : models 1 and 2. While model 1 regards the area as a single tectonic province, model 2 proposes two or more tectonic provinces, which are bounded by tectonic lines. Models 1 and 2 can be classified into models 1A and 1B, models 2A, 2B, 2C, and 2D, respectively. Model 1A hypothesizes an anticlinal bend of the Philippine Sea plate, which is being generated by the subductions along the Suruga and Sagami troughs. Model 1B emphasizes the crustal stress field generated by the collision of the Izu-Bonin volcanic arc with Japan arc and the slab-pull force along the Sagami trough. Since there are many local tectonic features that cannot be explained by model 1A or 1B, models 2A-2D were proposed. Model 2A divides the study area into two tectonic provinces : the northern province of compressive deformation by conjugate faults and the southern province of right-lateral shearing deformation. Model 2B divides the area into the eastern and western provinces, which are defined by sharp contrasts in the geologic structure, seismicity, crustal stress field, crustal movements, focal mechanisms of earthquakes, paleomagnetic directions, and volcanic activity. Many observations support the validity of the model 2B tectonic provinces. Model 2C introduces the hypothesis that the Izu-Bonin arc is being fractured into the inner and outer arcs because of a contrast in buoyancy. The existence of the estimated model 2C fracture, W est Sagami Bay Fracture, is still under debate. Model 2D regards the Higashi-Izu monogenetic volcano field, located in the eastern Izu Peninsula, as a field of crustal spreading. Model 2D proposes a key to understanding a sharp contrast in tectonic features between the eastern and western provinces of model 2B as well as the complex geometry of the Philippine Sea slab beneath the Japan arc.

著者

荒井 健一 小山 真人

出版者

特定非営利活動法人 日本火山学会

雑誌

日本火山学会講演予稿集 1996.2 (ISSN:24335320)

巻号頁・発行日

pp.25, 1996-11-05 (Released:2017-02-10)

著者

高木 圭介 青池 寛 小山 真人

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.3, pp.252-263, 1993-06-25 (Released:2010-10-13)

参考文献数

42

被引用文献数

2 3

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A synthesis of geological, geomorphological, and petrological data was made to reconstruct the tectonic evolution of the collision zone between the Honshu and Izu-Bonin Arcs during the middle to late Miocene time. The collision zone is composed of four allochthonous terranes, which are overlaid by syn-collisional trough-filling deposits. The four terranes, Izu, Tanzawa, Misaka, and Koma Terranes, were originated in the Izu-Bonin volcanic arc and have in turn collided with and accreted into the Honshu Arc at about 1, 5-3, 11, and 15 Ma, respectively. The geomorphology of the northern part of the Izu-Bonin Arc is characterized by two N-S trending ridges, Shichito-Iwojima and Nishi-Shichito Ridges, and Nishinoshima Trough between the two ridges. We interpret the Nishi-Shichito Ridge as a remnant volcanic arc of early Miocene age. The Nishi-Shichito Ridge was left by backarc rifting, which occurred between the Nishi-Shichito and Shichito-Iwojima Ridges during 15-10 Ma. The backarc rifting resulted in the increase of downdip angle of the Pacific plate slab and the eastward migration of the Izu-Bonin volcanic front. The rifting also generated along-arc compressional strain, which caused the intraarc deformation of the Shichito-Iwojima Ridge at about 10 Ma. This interpretation well explains the geologic history of each allochthonous terrane in the collision zone between the Honshu and Izu-Bonin Arcs as well as the present distribution of the allochthonous terranes.

著者

林 豊 小山 真人

出版者

歴史地震研究会

雑誌

歴史地震

巻号頁・発行日

no.18, pp.127-132, 2002

著者

角谷 ひとみ 井上 公夫 小山 真人

出版者

歴史地震研究会

雑誌

歴史地震

巻号頁・発行日

no.18, pp.133-147, 2002

被引用文献数

1

著者

小山 真人

出版者

日本情報地質学会

雑誌

情報地質 (ISSN:0388502X)

巻号頁・発行日

vol.5, no.2, pp.85-92, 1994

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地質学の専門家の「職人芸」を代替するシステム開発の第一歩として, 火山砕屑岩の成因推定に問題を限定した小規模な研究・教育支援システム<I>Volcaniclast</I>を試作・試用した.開発にはApple社のパーソナルコンピュータMacintoshと, その上で動くエキスパートシステム開発環境であるHyperpress社の<I>Intelligent Developer</I>をもちいた.<I>Volcaniclast</I>は, ルールベース, 事実 (ファクト) ベース, 推論エンジン, 対話型ユーザーインターフェースの4部分からなるルールベースシステムであり, 火山砕屑岩の成因推定にかんする知識を76のルールと11のファクトに格納している.典型的な野外地質データを入力した場合に, 正しい解答が最大の確信度をもって得られることを確認できた.このことから, すくなくとも<I>Volcaniclast</I>は学部レベルの学生教育用として十分な利用価値がある.

著者

早川 由紀夫 小山 真人

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.37, no.4, pp.167-181, 1992-10-01

被引用文献数

4

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The eruptive history of the Higashi Izu monogenetic volcano field for the past 32,000 years is revealed by tephrochronology and loess-chronometry. Morphology, color, and size of basaltic tephra grains are widely variable depending on the mode of the eruption; e.g., spinose red scoria are fallout from a strombolian eruption column when a scoria cone is established around the crater; yellowish green lapilli and hard tuff (kata) are products from phreatomagmatic explosions, the former being more magmatic than the latter. In the field, these discriminations are useful not only for identification of each tephra bed, but also for understanding the transition of eruptive styles during one eruptive event. Because vents are closed or sealed at the end of an eruption, an absolutely quiescence occurs between eruptive events in a monogenetic volcano field. This proves the validity of loess-chronometry. Some of the NW-SE or NE-SW trending alignments of volcanoes proved to be created by eruptive fissures; i.e., they are erupted simultaneously. Among them, the 11 km-long Iwanoyama-Iyuzan volcanic chain is the most conspicuous, which was active about 2,000 years ago. Eruptive events more than 10^9 kg of magma discharge are recognized 13 times during the past 32,000 years, so that the average frequency of eruption in this field is calculated one every 2,500 years. The last is the Iwanoyama-Iyuzan eruption. The discharge rate of magma is 100×l0^9 kg/ky for the past 32,000 years or 330×10^9 kg/ky for the past 5,000 years. The rate seems to be accelerated recently, however, it is still an order of magnitude lower than that of a polygenetic volcano such as Izu Oshima. The Kawagodaira eruption of 3,000 years ago is remarkable for two reasons: the largest with 765×10^9 kg of magma and the first appearance of rhyolite in the field.

著者

小山 真人

出版者

岩波書店

雑誌

科学 (ISSN:00227625)

巻号頁・発行日

vol.85, no.2, pp.182-193, 2015-02

著者

高橋 正樹 中山 芳美 小山 真人 荒牧 重雄

出版者

日本地質学会

雑誌

日本地質学会学術大会講演要旨

巻号頁・発行日

vol.93, 1986-04-25

著者

小山 真人 山岡 耕春 早川 由紀夫 白尾 元理

出版者

特定非営利活動法人日本火山学会

雑誌

日本火山学会講演予稿集

巻号頁・発行日

vol.1991, no.2, 1991-10-14

著者

小山 真人 早川 由紀夫 新井 房夫

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.40, no.3, pp.191-209, 1995-07-31

被引用文献数

4

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We reveal the eruptive history of the Higashi Izu monogenetic volcano field by tephrochronology and loess-chronometry and describe mainly volcanoes older than 32,000 years ago. The eruption of the volcano field started at about 150,000 years ago. Twelve tephra from volcanoes outside the Izu Peninsula were used as key beds. We found four eruptive fissures ; Takatsukayama-Sukumoyama, Kadono-Umenokidaira, Koike-Oike, and Numanokawa fissures, along each of which two to five monogenetic volcanoes erupted simultaneously. Interbedding of a distal wide spread tephra between eruptive deposits proper to the volcano field (the KIP-4 pumice between the Takatsukayama-Sukumoyama tephra, and the Hakone Da-4 pumice between the Kadono-Umenokidaira tephra) means that an eruption of a volcano outside the Izu Peninsula occurred simultaneously with the eruption of the volcano field. Vent locations of the volcano field were limited to the northern half of the present distribution during 80,000-150,000 years ago and were expanded in the later stage. Average frequency of eruption in the volcano field is calculated to be one/7,900 years for the period of 40,000-150,000 years ago, and one/2,500 years for the past 40,000 years. Average discharge rate of magma is calculated to be 0.64 kg/s before 40,000 years ago, and 2.5 kg/s for the past 40,000 years. Thus, both the average frequency of eruption and the magma discharge rate are higher for the past 40,000 years than those in the earlier stage. Many of the eruptions of andesite magma occurred later than 14,500 years ago, and the ones of dacite-rhyolite magma occurred only for the past 3,200 years. The cumulative pattern of the discharge mass of magma from the whole volcano field against time shows no clear predictability.

著者

小山 真人

出版者

Tokyo Geographical Society

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.108, no.4, pp.346-369, 1999-08-25

被引用文献数

4 14

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There remain many challenges in using historical documents to reconstruct a reliable history of earthquakes in Japan. Previous catalogs of historical earthquakes in Japan are not conclusive and contain uncertainties about date, hypocenter, magnitude, and tectonic interpretation of each earthquake. There is no database of digital texts of historical documents, which describe each earthquake. Since the density of historical records in Japan is temporally and spatially heterogeneous, seismologists should carefully remove apparent changes of earthquake frequency, which are caused by the heterogeneity of record density. There is, however, no detailed database of the density variation of historical records. The number of researchers, who are interested in historical earthquakes, is small.<BR>The situation stated above is caused mainly by the multi-disciplinary character of historical seismology. Japanese seismologists, who usually have little knowledge of history and classical literature, are not qualified to read a historical document and evaluate its reliability.<BR>The environment for research on historical seismology is, however, getting better. Japanese historians have published and are still publishing many historical documents, sometimes with translations into modern language. Evaluations of the reliability of each document can easily be done by referring to historical dictionaries or other databases. All these publications and information are available in many libraries. It is now easy and stimulating for many seismologists to read, evaluate, and interpret historical documents.

著者

小山 真人

出版者

日本地質学会

雑誌

日本地質学会学術大会講演要旨

巻号頁・発行日

vol.100, 1993-03-25