著者

Michael J. GROSSMAN 財城 真寿美 三上 岳彦 Cary MOCK

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.127, no.4, pp.457-470, 2018-08-25 (Released:2018-10-05)

参考文献数

34

被引用文献数

2

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歴史文書は,気象官署による測器を用いた公式気象観測が開始される以前の台風復元において,貴重な情報源となる。本稿では,1877年の日本(北海道,本州,四国,九州)に影響をおよぼした台風について,詳細な情報を含む5つの資料(1:日本で出版された英字新聞,2:歴史天候データベース,3:日本の灯台気象観測記録,4:イギリスおよびアメリカ合衆国の船舶の航海日誌,5:中央気象台の気象観測表)の検証を行った。そしてこれらすべての資料から,1877年において日本に上陸もしくは接近した4つの台風事例(6月11日,7月26-27日,8月25-27日,10月11日)が明らかとなり,歴史文書は,日本における暴風雨の位置,移動経路,風速,気圧,被害などに関する詳細な情報を含んでいることが裏づけられた。歴史文書に記録された台風に関する情報は,台風の襲来頻度や強度,挙動に関する理解を,気象観測や台風観測の詳細な数値データが十分に得られない過去の時代にまで,さかのぼる可能性を有しているといえる。

著者

西村 蹊二 斉藤 祥 谷岡 誠一 門脇 淳

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.86, no.6, pp.346-363, 1977-12-25 (Released:2009-11-12)

参考文献数

20

被引用文献数

1

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Detailed and intensive investigations have been carried out on the abrupt failure of submarine slope of a small island, Shin-jima, in Kagoshima Bay, Kyushu on April 1, 1975 by the joint research group of Geographical Survey Institute of Japan, Japan Maritime Safety Agency and Geological Survey of Japan under the sponsorship of Japan Science and Technology Agency.The Shin-jima island emerged from water at the great eruption of adjacent Sakurajima Volcano in 1779 to 1780 (An-ei Eruption) as one of central corns of Aira Caldera (MATSUMOTO, 1933). The island gradually reduced its exposed area by continuous wave erosion to form truncated configuration, being surrounded by broad, shallow, flat tidal bench.Geologically the island is composed of the latest Pleistocene to the earliest Holocene thick loose pumice deposits with intercalations of silt and clay showing inner bay facies. These formations are strongly faulted by eastwest faults. The surface of the island is covered with thin shell bed dominantly composed of Ostrea and andesitic lava. The flat bench around the Shin-jima consists of recent, loose pumiceous drift sand deposits derived from the island by wave erosion.The failure of the slope now in concern occurred at the spit of the southern tip of the island, where thickness of drift sand deposits attains at most about 35 meters according to sonic prospecting and borings at the spit. It was caused by submarine landslide in the thick, loose drift sand deposits. Volume of the slide mass amounts approximately 265, 000 cubic meters.The spit had formed steep submarine slope near critical angle by abundant supply of very loose drift sand from northern part of the island before the failure occurred. Neither sensible earthquakes nor volcanic activities of the Sakurajima which might have given significant effects to submarine landslide are observed and recorded in seismometer around the crucial moment of the failure.Therefore, the cause of the landslide is considered that the increase of load resulted from the deposition of drift sand attaining about 8, 400 tons in volume atop of the slope brought about decrease of safety factor of the slope to make it slide. Wave pressure seems to have triggered the slide because safety factor decreases about 20 % when fluctuation of pressure at the bottom caused by wave agitation is taken into account.

著者

小山 真人

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.4, pp.628-641, 1991-08-25 (Released:2010-11-18)

参考文献数

53

被引用文献数

3 5

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A brief review of paleomagnetic studies in the Philippine Sea and Izu-Bonin arc including the recent Ocean Drilling Program (ODP) results was made to clarify the present status and problems of the study on the tectonic evolution of the Philippine Sea plate. Paleomagnetic directions observed from the onland and marine areas on the Philippine Sea plate consistently show progressive increase of inclinations with time since the Eocene, and show large (30°-100°) clockwise deflections of declination in Eocene to middle Miocene rocks. These results suggest large clockwise rotation and northward drift of the whole Philippine Sea plate. This paper critically reviews all the models which have been proposed for the tectonic evolution of the Philippine Sea plate and proposes two possible reconstructions which can explain the paleomagnetic results.

著者

岩森 光 中村 仁美

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.121, no.1, pp.118-127, 2012-02-25 (Released:2012-03-05)

参考文献数

30

被引用文献数

4 5

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The generation and migration of geofluids in subduction zones are discussed for the subducting slab and the overlying mantle wedge and crust in terms of theoretical models and observations. Theoretical models include several mechanisms of fluid migration, e.g., Rayleigh-Taylor instability, Stokes ascent, channel flow, and porous flow, whose characteristic lengths and velocities differ significantly. As a result, these mechanisms may occur in different settings within subduction zones. We compare seismic and geochemical observations with the model of fluid migrations, based on which a typical fluid fraction within the mantle wedge is estimated to be 0.1 to 1 vol.%. Accordingly, it is suggested that fluid migration within the mantle wedge is driven by the buoyancy of the fluid, rather than being dragged by the flow of solid matrix. This suggests the fluid rises vertically. In the shallow part of the mantle wedge and within the arc crust, in particular the upper crust, the channel flow seems to be dominant. However, the relationship between these channels and the surface exits observed as volcanoes and hot spring systems is unclear. To better understand fluid distribution and migration, we need to incorporate more observations (e.g., electrical conductivity structure) and models (e.g., models of petrological and thermal structures).

著者

河本 大地

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.120, no.5, pp.775-785, 2011-10-25 (Released:2012-01-17)

参考文献数

40

被引用文献数

12 7

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Arguments on geoparks and geotourism have grown heated in recent years. However, few people can understand what “geo” means. This study considers how to share viewpoints of “geo” to build sustainable regional societies from a geographical perspective. First, the author defines geotourism as a type of ecotourism mainly focusing on the Earth's scientific resources. Second, the author argues that the concept of regional diversity proposed by the Japanese Geographical Union in 2005 is the core of Geography. The author has this concept connect the three existing concepts of the geosphere: biodiversity, cultural diversity, and geodiversity. Then, the author discusses promoting geotourism with the concept of regional diversity and familiar geographical views that are important for building sustainable societies. A geographical approach is inevitable for showing the relationship between our lives and “geo”. Humankind will have a better future by locating the geotourism as the main practice of “Earth Science for Society,” which was the slogan of the International Year of Planet Earth 2007-2009 (IYPE), and sustaining activities to develop ways of looking at “regional diversity”.

著者

大竹 政和

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.95, no.3, pp.167-185, 1986-06-25 (Released:2009-11-12)

参考文献数

55

被引用文献数

1

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The essential role of interstitial fluid pressure (pore pressure) in earthquake occurrence is strongly suggested by the observational fact that seismic activity was induced by water injection into a deep well and water impounding of an artificial reservoir. Elaborate studies related to water injection revealed following important characteristics of the induced seismicity : (1) Earthquakes are triggered to occur when the interstitial fluid pressure of the basement rock exceeds some threshold level ; (2) Focal mechanisms of induced earthquakes are in good harmony with the regional stress field ; and (3) Seismic activity propagates as far as several kilometers from the injection well. Based on those observational facts, we conclude that the injected water raising the interstitial fluid pressure releases the tectonic stress naturally accumulated. The effect of pressure change on the fracture strength of rock S is formulated in terms of the effective stress hypothesis asS=τ0+ (σn-P0) tanφwhere σn and P0 are normal stress and interstitial fluid pressure, and τ0 and φ are the coefficient of cohesive strength and internal friction angle, respectively. This criterion of rock fracture may also be applied to account for the reservoir induced seismicity. For the case of reservoir induced seismicity, however, the loading effect of water mass should be taken into consideration since some of the artificial reservoirs exhibit induced aseismicity.The effect of interstitial fluid pressure seems to be essential even for occurrence of natural earthquakes. Detailed studies on the Matsushiro earthquake swarm revealed that the earthquake swarm was brought about by the “water eruption”; high pressure water supplied at the depth beneath Matsushiro erupted to the ground surface accompanying a large number of small earthquakes which were generated by the increase of interstitial fluid pressure. Remarkable upheaval of the focal area, gushing out of large amount of water, and other associated phenomena are consistently interpreted by the water eruption model. It will be of great value for deeply understanding the nature of swarm activity to investigate whether such a mechanism is common or not to other earthquake swarms.The dilatancy-diffusion model of earthquake occurrence is briefly discussed from the viewpoint of the effect of interstitial fluid pressure. The model is a fascinating product of the effective stress hypothesis and results of laboratory experiments of rock fracture. It, however, is still dubious if the results obtained in the laboratory can directly be applied to the earthquake phenomenon occurring in the natural environment. We, therefore, emphasize the especial importance of advanced studies on induced earthquakes which occur under the half-natural and half-controlled circumstances.

著者

早坂 一郎

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.37, no.2, pp.69-84, 1925-02-15 (Released:2010-10-13)

参考文献数

31

著者

武内 寿久祢

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.105, no.5, pp.666-667, 1996-10-25 (Released:2009-11-12)

著者

吉井 敏尅

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.4, pp.393-398, 1993-08-25 (Released:2010-11-18)

参考文献数

18

被引用文献数

1 1

著者

田中 宏幸

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.125, no.5, pp.647-659, 2016-10-25 (Released:2016-11-18)

参考文献数

28

被引用文献数

2 2

---

Atmospheric and anti-electron neutrinos generated inside the solid Earth (geoneutrinos) are potentially powerful tools for imaging the Earth's interior, in order to visualize the spatial distribution of the density of uranium and thorium concentrations. This review is limited to neutrino imaging techniques. Observations of atmospheric neutrinos and geoneutrinos have been reviewed previously and are not discussed here. An elementary introduction to neutrino generation on the Earth and propagation through matter opens the review. After reviewing neutrino tracking methods in the context of today's views of technological developments, the current experimental limits on neutrino imaging are presented. A technique to confront the standard Earth model is discussed in the conclusion. Neutrino imaging of the Earth has been pursued at IceCube. It is fair to mention that it has opened the possibilities of this new elementary particle technique for the first time.

著者

松岡 憲知

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.125, no.1, pp.63-90, 2016-02-25 (Released:2016-03-22)

参考文献数

108

被引用文献数

6 5

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Following the development of high-resolution imaging, digital elevation models, thermal and hydrological data, and onsite ground information during the early period of the 21st century, the periglacial geomorphology of the Martian surface advanced rapidly. Images can even resolute meter-scale landforms, enabling identification of most periglacial features and analysis of their global distributions and detailed morphologies. This review focuses on progress in research covering permafrost distribution, patterned ground, possible heave and subsidence features, lobate debris forms, and slope-lineated features during the last decade. Most of the Martian high-latitude surface is underlain by ice-rich ground called the latitude-dependent mantle (LDM), which favors permafrost-related features possibly developed under warm-humid conditions during past high-obliquity periods or partially s,till active under the present cold-dry conditions. Thermal contraction cracking is likely to prevail in the LDM, resulting in high-centered, flat-top polygons, possibly underlain by sublimation-type wedges or sand wedges that prevail at high latitudes. The surface patterns change into subdued or peak-top polygons toward the mid-latitudes, probably reflecting long-term sublimation of the LDM. Some researchers attribute stone circles to sorting due to freeze-thaw, but the features are much larger than candidates on the Earth. Small isolated domes with concentric cracks or craters at the top may include pingos, which also prevail at high- to mid-latitudes. Asymmetrical scalloped depressions may result from sublimation or thawing of the LDM, but there is a debate between pole-ward and equator-ward slope retreats. Lobate debris aprons may originate from creep of ice-rock mixtures or debris-covered glaciers, but the distinction between the two origins is unclear, as in the long-lasting debate on terrestrial candidates. Some thin, smaller debris lobes at high latitudes resemble stone-banked solifluction lobes on the Earth, which may indicate the occurrence of seasonal freeze-thaw cycles in the recent past. Time-series images indicate active slope features, including gullies, slope streaks, and recurrent slope lineaes that develop below cliffs. These active features may originate from outflows of brine that thaws far below the melting point of water ice.

著者

菊地 徹

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.67, no.2, pp.94-103, 1958-06-30 (Released:2009-11-12)

著者

鶴岡 弘 大竹 政和

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.2, pp.256-267, 2002-04-25 (Released:2009-11-12)

参考文献数

34

被引用文献数

2 6

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We conducted a numerical simulation to clarify the effects of the earth tide on earthquake occurrence. In the simulation, fault planes, having different initial stresses, are loaded by constantly increasing tectonic stress and cyclic stress due to the earth tide. Earthquakes are assumed to occur when the shear stress reached a certain threshold level. The result of the simulation indicates that the tidal effect on earthquake occurrence is strongly controlled by the ratio of stress change rate between earth tide and tectonic stress accumulation; earthquakes concentrate near phase angle 0° (maximum tidal stress) when the ratio is large, and they are distributed with a peak around-90° (maximum acceleration of tidal stress) when the ratio is small. This phase selectivity is very similar to the observations of tidetriggered earthquakes reported so far, and rock failure experiments under cyclic loading, suggesting that our approach may provide an important clue for clarifying the physical mechanism of tidal triggerings of earthquakes. Schuster's test has been widely used for detecting tidal effect on earthquake occurrence. However, it is shown by the numerical simulation that the result of a test strongly depends on the size of a data set when earthquakes have phase selectivity by nature, and that Schuster's p-value is not appropriate to represent the strength of tidal effects. Alternatively, we propose to use α, which is the amplitude of a sine curve fitted to the frequency distribution of earthquakes against phase angle, to evaluate the strength of tidal effects. We also emphasize that the effect of ocean loading is an important component of the earth tide, and cannot be neglected in a study of tidal triggerings of earthquakes.

著者

荒井 章司

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.119, no.2, pp.392-410, 2010-04-25 (Released:2010-07-06)

参考文献数

87

被引用文献数

7 9

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Various characteristics of podiform chromitites, an enigmatic mantle rock member, are reviewed in this article. Chromitites are composed of chromian spinel, with the general formula (Mg, Fe2+)(Cr, Al, Fe3+)2O4, and silicates (mainly olivine). The Fe3+ content is generally very low, being less than 0.1 to all trivalent cations, in mantle chromian spinels. The Mg/(Mg + Fe2+) ratio (= Mg#) changes inversely with the Cr/(Cr + Al) ratio (= Cr#), which increases with an increase of degree of partial melting of mantle peridotites. The Cr# of chromian spinel is generally higher than 0.4 (generally 0.6 to 0.8) in podiform chromitites, varying widely from 0.1 to 0.9 in the mantle peridotite. The podiform chromitite forms pod-like bodies (dimensions of up to 1.5 km × 150 m for an individual pod) with a dunite envelope, totally set within mantle harzburgite. In well-preserved ophiolites, they occur in the uppermost mantle, especially in and beneath the Moho transition zone, which is dominated by dunite. The Cr# of chromian spinel is relatively low (0.4 to 0.6) around the Moho transition zone, and high (>0.6) at deeper levels in the mantle section. Chromitites are denser and less anisotropic in Vp than peridotites, and the Vp is 8.5 to 9 km/sec depending on the proportion of chromian spinel, and higher in the former than in the latter.  The podiform chromitite has been interpreted to be one of melt/rock interaction products within the uppermost mantle harzburgite; hybridization of relatively Si-rich melt formed by the breakdown of orthopyroxenes of the wall harzburgite and subsequently supplied primitive melt cause oversaturation in chromian spinel, giving rise to formation of chromitite with a dunite envelope. The fractionated melt leaving high-Cr# podiform chromitite is possibly of arc-magma affinity. Chromitites with low-Cr# (0.4 to 0.6) chromian spinel can be in equilibrium with MORB. Recently found ultra-high pressure minerals, such as diamond, moissanite, Fe-silicides and Ni-Fe-Cr-C alloys, within chromian spinel of podiform chromitites make the genetical history of chromitites highly enigmatic. A new story, which incorporates the genesis and involvement of these highly reducing, ultra-high pressure minerals, is required.

著者

西野 寿章

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.123, no.2, pp.298-314, 2014-04-25 (Released:2014-05-16)

参考文献数

46

被引用文献数

3

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The purpose of this paper is to clarify the history and the characteristics of electric utility companies in Tokyo. In 1887, the first electricity supply company in Japan was established in Tokyo. In 1933, there were 818 electric utility companies. Before World War II, two or more electricity supply companies supplied one region, and there was tough competition to supply electricity to the Tokyo area. In 1938, the principle of free competition was replaced by nationwide management by the pre-war military government. Tokyo Electric Power Company was established in Tokyo by the Potsdam government ordinance in 1951, and the right to supply electricity to a region was limited to one company. Disproportionate electricity demand and amount of power generated is a historical characteristic of electric utility companies operating in Tokyo. The rate of self-sufficiency of electricity in Tokyo was 15 percent in 1931, and it was three percent in January 2012. The power generation and electric supply system began to be discussed after the nuclear plant disaster caused by a major earthquake on March 11, 2011 at Fukushima. In August 2011, the Tokyo Metropolitan Government Office began to examine constructing a large-scale power plant fueled by natural gas.As the population of Japan decreases, revenues will decline. Before World War II, Tokyo City's managed electric utility obtained high earnings constantly. These high earnings were a very important and stable source of income for the local government. The system of the electric utility companies in Japan before World War II could provide a model for a reorganized electricity supply system in the future.

著者

國松 豊

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.6, pp.798-815, 2002-12-25 (Released:2009-11-12)

参考文献数

102

被引用文献数

2 3

---

The human lineage is a branch of the huge evolutionary tree of the Hominoidea, which today includes ourselves, chimpanzees, gorillas, orangutans, and gibbons. All extant hominoids, except for the single world-wide species Homo sapiens, are now endangered and restricted in their distribution to tropical/subtropical forests of Africa and Southeast Asia. However, hominoids were once a more flourishing group millions of years ago. In the Miocene, there were various kinds of hominoid primates, and their distribution was much wider than today, from the southern tip of Africa through Arabia, to Europe in the west and through India to China in the east. It is from this great diversity of Miocene hominoids that the earliest human ancestors emerged, probably during the Late Miocene. The first part of this article provides readers with general information about extant hominoids. The second part is devoted to Miocene fossil hominoids with emphasis on African fossils. Although the main subject of this article is fossil hominoids, some recent findings of early hominids are also mentioned to at the end.

著者

河合 研志 内出 崇彦

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.128, no.3, pp.465-475, 2019-06-25 (Released:2019-07-11)

参考文献数

23

被引用文献数

1

---

Teaching materials on determining epicenters using P-wave lateral polarity data were produced. These materials are intended for use in secondary and advanced education and only require inexpensive tools such as a ruler and a protractor; they do not require specialized software or devices. The materials consist of PDF files containing three-component waveform data before and after P-wave arrivals for 929 small events recorded at Hi-net stations in the Hida region, central Japan, from February 1 to April 30, 2011. A P-wave lateral polarity analysis using the two horizontal components provides information on seismicity in the Hida region before and after the March 11, 2011 off the Pacific coast of Tohoku Earthquake. Students can discuss temporal changes in the underground stress state based on their analyses. Depending on the grade and science education level of students, the time-series waveform data allow them to conduct additional exercises such as error analyses and epicenter determinations using S–P differential travel time, as well as geophysical interpretations of results.

著者

早川 裕一 松倉 公憲

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.112, no.4, pp.521-530, 2003-08-25 (Released:2009-11-12)

参考文献数

26

被引用文献数

7 11 1

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The mean recession rate of Kegon Falls is examined, estimating original location and age. Two locations (LI and LII) at which the waterfall originated are estimated based on the distribution of Kegon lava, while the age of origination is considered to be the same as that of the Kegon lava eruption, i.e., 20, 000 years ago. Two values of the mean recession rate obtained are 0.018 m/y for the case of LI and 0.10 m/y for the case of LII. On the other hand, the recession rate can be evaluated, as an order estimation, using the empirical equation of the authors (Hayakawa and Matsukura, Earth Surf. Process. Landforms, 28, 2003), which shows relationships between the recession rates of waterfalls and the ratio of the erosive forces of rivers to bedrock resistance. The values of parameters used in the index of force/resistance ratio are obtained from existing data and field measurements for Kegon Falls. Substituting them into the equation, the recession rate is calculated to be in the order of 0.009-0.019 m/y. This result suggests that the recession rate for the case of LI is suitable for Kegon Falls.

著者

鈴木 和恵 丸山 茂徳 山本 伸次 大森 聡一

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.119, no.6, pp.1173-1196, 2010-12-25 (Released:2011-03-17)

参考文献数

48

被引用文献数

20 35

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The Japanese Islands have long been considered to be the most evolved of all the island arcs in the oceans. A simple scenario has been implicitly accepted for the growth of the Japanese Islands: since subduction started sometime around 520 Ma, the TTG crust has increased over time in association with the steady-state growth of the accretionary prism in front. Here, we show very different dynamic growths of TTG crusts over time than previously thought, i.e., four times more TTG crusts than at present must have gone into the deep mantle due to tectonic erosion, which occurred six times since subduction was initiated at 520 Ma. Tectonic erosion is a major process that has controlled the development history of the Japanese islands. It can be traced as a serpentinite mélange belt, which indicates the upper boundary of past extensive tectonic erosion.

著者

山上 萬次郎

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.26, no.11, pp.851-862, 1914-11-15 (Released:2010-10-13)