著者

高野 修 西村 瑞恵 藤井 哲哉 佐伯 龍男

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.118, no.5, pp.776-792, 2009-10-25 (Released:2010-03-19)

参考文献数

28

被引用文献数

21 18

---

Since previous research revealed that most of the methane hydrates in the eastern Nankai Trough area occur in matrix pores of turbidite sandstones, the facies distribution of turbidite sandstones may be one of the important keys to evaluate the distributions and actual volume of methane hydrates in the eastern Nankai Trough area. This paper attempts to reconstruct depositional processes of submarine-fan turbidites, and examines the relationship between turbidite facies distributions and bottom simulating reflector (BSR) occurrence as a proxy of methane hydrate using sedimentologic and sequence stratigraphic methodology. First, 2D/3D seismic survey data and well data including cores and logs were used to identify turbidite facies, seismic facies, and depositional sequences. The targeted Plio-Pleistocene Kakegawa and Ogasa Groups can be divided into 17 depositional sequences, and include six seismic facies indicating submarine-fan elements and surrounding slope to basin-floor environments. Next, facies maps for each depositional sequence unit were created by plotting all information on seismic facies, 3D seismic geomorphology, and well facies data. The obtained facies maps reveal that 11 major submarine canyons functioned as positionally fixed sediment supply systems from main land Japan, along which submarine fans were formed in the forearc basins. Submarine-fan depositional styles changed through Plio-Pleistocene from a braided channel type, through small radial fan, trough-fill fan, and muddy sheet fan types, to a channel-levee system type. Finally, the facies maps of each depositional sequence were overlaid with the BSR distribution. The overlaid maps indicate that the BSRs occur on feeder channels, distributary channels, and proximal lobes of submarine fans, suggesting that methane hydrates selectively occur in coarser grained portions of a submarine fan. Because the lower part of the Kakegawa Group is mainly composed of braided channel-type submarine fan turbidites, the lower Kakegawa horizon serves one of the major horizons bearing methane hydrates in the eastern Nankai Trough area.

著者

小熊 宏之 井手 玲子 雨谷 教弘 浜田 崇

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.1, pp.93-104, 2019-02-25 (Released:2019-04-03)

参考文献数

18

被引用文献数

5 5

---

The vulnerability of alpine ecosystems to climate change, as pointed out by the Intergovernmental Panel on Climate Change (IPCC), and the necessity to monitor alpine zones have been recognized globally. The Japanese alpine zone is characterized by extreme snowfall, and snowmelt time is a key factor in the growth of alpine vegetation. Therefore, in 2011, the National Institute for Environmental Studies (NIES), Japan, initiated long-term monitoring of snowmelt time and ecosystems in the Japanese alpine zone using automated digital time-lapse cameras. Twenty-nine monitoring sites are currently in operation. In this study, images from the cameras installed at mountain lodges in Nagano Prefecture and around Mt. Rishiri in Hokkaido are used. In addition, live camera images are obtained from cameras already operated by local governments in the Tohoku area and near Mt. Fuji. Red, green, and blue (RGB) digital numbers are derived from each pixel within the images. Snow-cover and snow-free pixels are classified automatically using a statistical discriminate analysis. Snowmelt time shows site-specific characteristics and yearly variations. It also reflects the local microtopography and differs among the habitats of various functional types of vegetation. The vegetation phenology is quantified using a vegetation index (green ratio) calculated from the RGB digital numbers. By analyzing temporal variations of the green ratio, local distributions of start and end dates and length of growing period are illustrated on a pixel base. The start of the green leaf period corresponds strongly to the snowmelt gradient, and the end of the green leaf period to vegetation type and elevation. The results suggest that the length of the green leaf period mainly corresponds to the snowmelt gradient in relation to local microtopography.

著者

尾野 作次郎

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.51, no.12, pp.551-560, 1939-12-15 (Released:2010-10-13)

著者

小原 一成

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.112, no.6, pp.837-849, 2003

被引用文献数

5 14

---

Non-volcanic deep low-frequency tremors detected in southwest Japan are distributed in the forearc side along the strike of the descending Philippine Sea plate. The source depth of the tremor corresponds to the slab interface or the Moho discontinuity. The time sequence of the tremor activity is characterized by long durations from hours to weeks. The mobility and the successive occurrence of the tremor are thought to be related to the existence of fluid liberated from the slab by a dehydration process. The spatial distribution of the tremors is not homogeneous in a narrow belt but is spatially clustered. The major activity of the tremors with relatively long time durations is also clustered periodically, with a period of 2-3 months in the east and middle of Shikoku area and about 6 months in the west of Shikoku. On the other hand, tremors are sometimes triggered by local earthquakes or teleseismic waves. The periodicity of the tremor activity may represent a stable accumulation of fluid with a stable subduction process and the triggering phenomenon implies the unstable condition of the occurrence of tremors.

著者

鷺谷 威 大坪 誠

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.5, pp.689-705, 2019

被引用文献数

4

---

<p> Geodetic estimates of crustal strain rates in the Japan islands were an order of magnitude larger than geological/geomorphological estimates, which has been an unresolved problem called the strain rate paradox. Ikeda (1996) postulated that geodetic strain mainly reflects elastic strain accumulation due to interactions at plate boundaries. This hypothesis was proven to be correct by the occurrence of the 2011 <i>M</i>_W 9.0 Tohoku-oki earthquake. Confusion between elastic strain and inelastic strain was the cause of the paradox. Significant postseismic deformation observed after the Tohoku-oki earthquake made it possible to distinguish the inelastic contribution from the geodetically observed crustal strain through a comparison with the pre-seismic strain rate pattern, which promoted a better understanding of inelastic deformation in the Japan islands. On the other hand, migration of localized deformation and temporal changes of strain rate are identified over a geological time scale, implying that it is essential to carefully review the methods and the uncertainties of geological/geomorphological strain rates. An integrated understanding of crustal deformation in the Japan islands is being advanced through detailed investigations of crustal strain rates on variable temporal and spatial scales.</p>

著者

星埜 由尚

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.129, no.2, pp.155-160, 2020

被引用文献数

3

著者

山田 直利 矢島 道子

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.2, pp.257-267, 2016-04-25 (Released:2016-05-12)

参考文献数

9

---

Edmund Naumann (1854–1927), the first professor of the Geological Institute, Science Department, the University of Tokyo, presented a proposal to found the Geological Survey of Japan to Hirobumi Ito, Minister of the Home Affairs of Japan, in 1879. The Japanese Government immediately accepted this proposal, so Naumann resigned his post as a professor of the university and returned to Germany, in order to find the necessary specialists and items for the upcoming survey. During his stay in Germany, on January 3rd, 1880 he gave an invitation lecture on Japan, which was published in “die geologische Verhandlungen der Gesellschaft für Erdkunde zu Berlin” as a paper titled “Ueber die wirthschaftlichen Verhältnisse Japans und die geologische Aufnahme des Landes” (The economic situation of Japan and the Geological Survey of Japan). This paper introduced the feudal system, which had controlled Japan through the Middle to Modern ages, the economic situation of Japan after the Meiji Restoration, especially for agriculture, means to promote Japanese agriculture and industry, and the purpose and tasks of the Geological Survey of Japan. The paper, which we have now translated into Japanese, is important because it is similar to the Japanese translation of the above proposal handwritten in 1879, and the original text of the proposal, probably written in German, has now been lost.

著者

日下部 四郎太

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.18, no.6, pp.393-403, 1906-06-15 (Released:2010-10-13)

著者

大石 太郎

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.115, no.4, pp.431-447, 2006-08-25

参考文献数

34

被引用文献数

1

---

After 1969 when the French language became one of Canada's two official languages its sta tus gradually improved. In particular, the Canadian Charter of Freedom and Human Rights, included in the Constitution Act 1982, and the Mah&eacute; case heard by the federal Supreme Court in 1990 as a clarification of the charter promoted improvements to the education system for francophones outside Quebec. In other words, institutional support for francophones has been developed especially in the realm of education. While traditional francophone communities outside Quebec are mostly situated in rural and remote areas, francophone communities have been developed in English-dominant Canadian cities as a result of migration. This study, therefore, attempts to examine language maintenance of francophones and development of their community in the Halifax region, Nova Scotia, as a case of English-dominant Canadian cities, based on the author's field survey carried out in 2003, and which included some interviews.<BR>Concerning the demolinguistic situation in Nova Scotia, an analysis of census data from 1951 to 2001 confirms that the French mother tongue population and the bilingual population in Halifax County increased. In addition, age composition among francophones in Halifax County is much healthier than that of traditional francophone counties.<BR>Most francophones in the Halifax region were born in Quebec or the Maritimes, and moved to the Halifax region to work or enter university, and in some cases, met their future spouses there. Because Halifax is the most important city in Atlantic Canada, many departments and agencies of the federal government have a regional office. Consequently, there are many job opportunities for bilingual people. As a result, it is natural for francophones to work in the Halifax region as bilingual. In 1991, a French school and francophone school board was established in the Halifax region : finally the provincial-wide francophone school board was established in 1996. Of course, education is an important factor for language maintenance. However, the francophones in the Halifax region who want their children to keep the French language not only send their children to a French school in the region, but also make them speak French in conversations with the family members. Much effort is required to keep the French language in English-dominant Canadian cities. However, they succeeded in overcoming these difficulties and developing their community.<BR>Previous studies on language maintenance emphasized institutional support such as education, and its importance is clear in this study. However, institutional support since the 1980s in Nova Scotia seems to be belated in rural and remote areas. On the other hand, the social characteristics of the francophones in the Halifax region make institutional support effective.

著者

片岡 龍峰

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.119, no.3, pp.519-526, 2010-06-25

参考文献数

16

被引用文献数

1 1

---

&emsp;Possible influences of cosmic rays on terrestrial climate have been studied by many researchers since a good correlation between neutron monitor counts and global cloud amount was reported by Svensmark and Friis-Christensen in 1997. The cosmic ray-cloud relationship may be best tested during Forbush decrease events, in which cosmic rays largely decrease for several days associated with coronal mass ejections. Some cloud parameters are likely to respond to the transient decrease of cosmic rays with a typical time delay of several days, although we do not know the physics behind the cosmic-ray cloud relationship.

著者

宮原 ひろ子

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.119, no.3, pp.510-518, 2010-06-25

参考文献数

20

被引用文献数

1 3

---

&emsp;The relationship between solar activity and climate change in the past can be examined using proxy records. Variations of solar activity can be reconstructed based on carbon-14 in tree rings, which are produced by galactic cosmic rays modulated by the solar wind, while climate change can be reconstructed from changes of tree-ring growth rate or content of stable isotopes in ice cores from the polar region. A comparison of solar activity and climate change at the Maunder Minimum in the 17^th century and the Early Medieval Maximum Period in the 9-10^th century suggests that the sun plays an important role in climate change even on a decadal time scale. The characteristic variations detected in climate change suggest the mechanism of solar influence on climate involves galactic cosmic rays. Variable features of eleven-year and twenty-two year cycles of solar activity and consequent variations of cosmic rays are possible origins of complex variations of climate change on decadal to multi-decadal time scales. We summarize variations of solar activity and cosmic rays during the past 1200 years and their possible influence on climate change.

著者

山岡 耕春 中禮 正明 安藤 雅孝

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.2, pp.185-191, 2002-04-25

参考文献数

9

被引用文献数

2

---

The temporal relationship between the interplate and inland earthquakes of Kyushu Island region was investigated. We analyzed this relationship by stacking the temporal frequency of the inland earthquakes with reference to the occurrence time of each major interplate earthquake in the Hyuga-nada region, that occurred between 1900 and 2000. A good coincidence of occurrence between the inland and the interplate earthquakes is recognized. While the tendency of the occurrence after the interplate events has already been pointed out, we found that the inland earthquakes also tend to occur before the interplate events. Abrupt activation of the inland earthquakes within several months before major interplate earthquakes is recognized in addition to the tendency to occurr afterwards. The preceding inland earthquakes may indicate that they are triggered by precursory slow slips around the hypocenters of the Hyuga-nada earthquakes.

著者

渡辺 光

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.61, no.1, pp.1-7, 1952

被引用文献数

2

---

This article presents a basis for the subdivision of Japan into landform divisions, and to proceed to give the names and locations of the divisions. The fundamental premise in determining landform divisions is a fact that Japan is a single structural and geomorphologic unit from the world or the continental viewpoint, and the whole country is included in the Circum-Pacific Orogenic Zone. Therefore, the orogenc processes that have had much to do in forming the major landforrn features are considered to be the fundamental basis for determining the primary landform units.<BR>The following four primary landform divisions or Regions are differentiated by essential difference in recent orogenic movements, landform features, structures and means of coalescence of those arcs. They are ; A) Hokkaido Proper Region B) Northeast Region C) Central Region D) Southwest Region. The latter three regions are each composed of two or more subregions which coincide with the major tectonic units. Each traditional tectonic unit is taken as an independent subregion. These regions and subregions in turn are divided into districts on the basis of the differing effects of endogenic processes such as natures and amount of earth movements or volcanic activities. The districts are again divided into Sections en the basis of minor landform features resulting from either endogenic or exogenic processes. According to the above items, four regions, eight subregions, 51 districts and 240 sections have been established.

著者

渡辺 光

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.69, no.4, pp.145-152, 1960

被引用文献数

1

---

As premises for main topics of inquiries, a brief review is made of the status of the wartime geography in Japan which should seem to have a direct bearing on the later development of this field. There, the oversea expeditions, war-time researches, and &ldquo;Geopolitik&rdquo; at their time, and their later influences are pointed out.<BR>Status of Geography since 1945 is elucidated according to the following headings.<BR>1) Various kinds of national land surveys in connection with the various land planning projects.<BR>2) Promotion of international intercourse.<BR>3) Establishment of departments of geography in universities and colleges throughout the country.<BR>4) Dispatch of oversea scientific investigation parties.<BR>5) Propulsion of joint studies by workers of various fields of geography, and participation of geographers in various interdisciplinal studies.<BR>6) Problems waiting for future solution.

著者

馬場 知哉 柿澤 茂行 森 宙史 車 兪澈 黒川 顕 大島 拓

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.129, no.6, pp.805-824, 2020-12-25 (Released:2021-01-18)

参考文献数

103

被引用文献数

3

---

Estimating the “minimal gene set” for a cell to be viable is an important issue in understanding “living” cells, creating “artificial” cells, and revealing “ancient” cells. The minimal gene set is critical information for understanding a cell system and designing an artificial genome, which is an essential element for creating an artificial cell. Artificial cells can provide many clues to understanding primordial life on Earth. To reveal minimal gene sets, “essential genes” in many bacteria, which could not be removed from bacterial genomes, have been identified. Bacteria are the most useful organisms for identifying essential genes from their specific characteristics: small genomes, rapid growth, and species that are easy to manipulate genetically. Therefore, various investigations on minimal gene sets or minimal genome of bacteria are reviewed, and “the minimal gene set for a viable cell” is discussed.

著者

下司 信夫

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.2, pp.175-189, 2018-04-25 (Released:2018-06-11)

参考文献数

47

被引用文献数

2 2

---

The fundamental structure of a collapse caldera is subsidence of a block(s) into a magma chamber with the evacuation of a massive volume of magma from the chamber. Decompression of a magma chamber caused by the extraction of magma from a magma chamber coinciding with pyroclastic eruption, effusive eruption, and lateral magma migration drives caldera collapse. Caldera-forming eruptions exhibit wide variations. Caldera-forming pyroclastic eruptions are characterized by a high eruption rate, whereas caldera-forming effusive eruptions have a much lower effusion rate. Caldera collapse caused by a pyroclastic eruption generally occurs within one day, whereas incremental collapses continue for up to one month in the case of some effusive eruptions. Collapse calderas also have wide structural variations. The aspect ratio of the roof of the magma chamber controls the development of caldera faults. The development of multiple caldera faults with a high aspect ratio causes piecemeal collapses, whereas a low aspect ratio results in the subsidence of coherent blocks detached by a simple ring fault. With the progress of caldera subsidence, the caldera structure develops from a flexural down sag to a double-ring fault system, and finally reaches an upward-flaring “funnel shaped” caldera following an intense collapse of the caldera wall. Calderas vary widely in size from 1 km to 100 km, and can also be divided into at least three classes by their internal structures. The largest group of more than 20 km across is characterized by flexural down-sag deformation. The intermediate-size group is characterized by well-developed caldera-border faults. The smallest calderas of less than 10 km across may have piecemeal structures. The existence of a pre-caldera volcanic edifice is also an indicator of differences in the magmatic system. Some calderas form at the summit of a pre-existing stratovolcano or shield volcano, whereas some large calderas form in a cluster of small volcanoes, involving non-volcanic basement rocks. A structural model of caldera development should involve these wide spectrums of collapse calderas. The development of collapse calderas is controlled by variations of magmatic activity, such as eruption style, eruption rate, and duration of eruption, as well as the architectures of their magma storage systems.

著者

野坂 俊夫

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.117, no.1, pp.253-267, 2008-02-25 (Released:2010-02-10)

参考文献数

51

被引用文献数

2 2

---

Gabbroic rocks recovered from deep holes in the oceanic crust significantly vary in the abundance and assemblage of alteration minerals, showing a close association with the original lithology and distribution of dikes and veins. The mineralogical variation is considered to reflect the durability of primary minerals, accessibility and composition of alteration fluids, and alteration temperature. Textural relationships of alteration minerals suggest a common cooling history of oceanic gabbros from granulite or pyroxene hornfels facies to zeolite facies conditions. It is considered that regardless of spreading rate, the static formation of upper greenschist- to lower amphibolite-facies minerals is the dominant alteration process at the lower crust near oceanic ridges, whereas subgreenschist-facies alteration represents the exhumation histories of gabbroic masses from depth. High-temperature plastic shear zones with almost anhydrous recrystallization of primary minerals develop locally at slow-spreading ridges, and possibly provide pathways for later hydrothermal fluids. In contrast to the gabbroic rocks, oceanic peridotites have a monotonous mineralogy formed during low-temperature serpentinization processes, making it difficult for us to depict their cooling histories or in-situ alteration processes at the upper mantle. The hypothesis that oceanic Moho represents a serpentinization front in peridotites is suitable for the uniformity of crustal thickness inferred from seismological observations, but lacks a rationale for supplying a constant amount of water to the upper mantle or for the cessation of serpentinization at a constant degree. Alternatively, preferential alteration of pyroxene at relatively high-temperature conditions might form the oceanic crust of uniform thickness.

著者

舟田 久之

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.101, no.6, pp.491-505, 1992-12-05

参考文献数

18

被引用文献数

1 1

著者

小林 貞一

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.56, no.5, pp.151-185, 1944-05-15 (Released:2010-10-13)

出版者

公益社団法人 東京地学協会

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.13, no.4, pp.244a-246, 1901