地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
117 巻 , 3 号
選択された号の論文の16件中1~16を表示しています
表紙
速報
  • 林 愛明, 賈 東, 任 治坤, 呉 暁俊
    2008 年 117 巻 3 号 p. 593-598
    発行日: 2008/06/25
    公開日: 2010/05/14
    ジャーナル フリー
     2008年5月12日チベット高原と四川盆地の境界部でMw 7.9ブン川地震が発生し(図1),中国の中部から西部にかけて広い地域で大規模な被害をもたらした。6月4日現在,中国政府の公式発表による死者の数は69,122人,負傷者373,606人,行方不明者17,991人となっている。この地震の震源断層のメカニズムと地表地震断層を含む地震に関連する地表の変形特徴と被害との関係を解明するために,私たちの調査グループは地震の2日後に震源地に入って,9日間にわたって調査を行った。ここで今回の調査で得られた成果の一部を報告する。また,今回の地震で亡くなられた方々に対し哀悼の意を表するとともに,被災された方々に心からお見舞い申し上げたい。
論説
  • 石原 肇
    2008 年 117 巻 3 号 p. 599-616
    発行日: 2008/06/25
    公開日: 2010/05/14
    ジャーナル フリー
     The purpose of this research is to investigate how the Anti-disaster Headquarters of Tokyo Metropolitan Government has executed restoration measures for mudflow damage caused by volcanic activity on Miyake Island since June 2000. Most of the restoration of the major ring road along the coast was conducted during the first period from April 2001 to March 2002, aiming at securing the fundamental transportation system for living and reconstruction activities, water and energy supply, communication, and others. The second period from April 2002 to March 2004 was directed for the restoration of other roads including paths that access inland woodlands, and the construction and maintenance of a large number of erosion-control facilities in gullies dissected by volcanic activity. Similar restoration measures were continued and extended to parts of the interior and upstream zones, where watershed management works were also started during the third period from April 2004 to March 2006. In sum, the countermeasures policy for disaster restoration first gave priority to the restoration of roads, particularly those along the coast at first, then shifted attention to the construction and maintenance of erosion-control facilities in and along inland gullies, followed by watershed management works in upstream zones. The sequential and areal shifts of targets of countermeasures for disaster restoration have been made with a perception change among administrative bodies that recognized the effects of volcanic gases as the major object to be controlled in the volcanic disaster as a whole.
  • 河本 大地
    2008 年 117 巻 3 号 p. 617-636
    発行日: 2008/06/25
    公開日: 2010/05/14
    ジャーナル フリー
     The aim of this study is to examine to what extent the introduction of organic farming methods, typical post-productivism in agriculture, affects changes in plantation agriculture, the typical productivism in the Global South. A case study was conducted on the tea industry in Sri Lanka. The method was intensive interviews with key persons at the headquarters of plantation companies, management sections of tea estates, relevant organizations, and with some tea estate residents, as well as collecting relevant documents in July, August, and December, 2005.
     The findings are as follows. Firstly, the tea industry in Sri Lanka, particularly the plantation estate sector, has structural problems in terms of environment, economy, and social sustainability. These problems have been mainly caused by decreasing consumption of tea in industrialized countries and former policies of nationalizing Sri Lankan tea estates.
     Secondly, organic farming methods in tea plantation estates have been introduced mainly in disadvantaged mountainous areas, characterized by many abandoned tea areas and old tea bushes. Organic farming is an alternative strategy for developing the estates in such areas.
     These organic tea estates are trying to brand themselves, diversify crops, promote biodiversity, conduct eco-tours of estates, enhance social welfare system for residents, and introduce fair-trade certifications, as well as obtain organic certifications. Thus, organic farming in the tea estates can be understood as a strategy of diversified management, which is a combination of the elements of post-productivism.
     However, the cost of production (COP) is higher in organic tea estates than in conventional estates, especially the cost of composting and weeding. Due to their labor-intensive character, organic estates are affected enormously by increasing labor costs, and in the near future the outflow of labor might also be a problem. These issues are common in the Sri Lankan tea industry.
     Moreover, marketing to acquire new consumers in industrialized countries is not easy for organic estates, and the bought price is not increasing. This trend will not lead to the establishment of more organic tea estates. Some existing organic estates are also on the verge of closure under these circumstances.
     To ensure the sustainability of organic tea estates, it is necessary to expand their social welfare policies especially for younger residents, and communicate these efforts to society along with environmental conservation policies. Moreover, consumers in industrialized countries need to understand and support the challenges affecting disadvantaged estates.
短報
  • 鈴木 郁夫, 太田 陽子, 吾妻 崇
    2008 年 117 巻 3 号 p. 637-649
    発行日: 2008/06/25
    公開日: 2010/05/14
    ジャーナル フリー
     The area at the middle to lower reaches of the Shinano River is a well-known major Neogene thrust and fold belt in Japan. Deformed fluvial terraces, such as anticlinal ridges, synclinal valleys, and fault scarps along the Shinano River, provide a good record of recent tectonic activity in this belt. A large exposure (ca. 150 m long, and up to 10 m deep) was excavated by construction work on the eastern limb of the Tokimizu anticline, giving us an opportunity to observe various types of fault geometry.
     Four faults—F1, F2, F3, and F4—cut terrace deposits of ca. 130-150 ka (Koshijippara terrace) and underlying early Pleistocene Uonuma Formation. The westernmost fault, F1 is represented as a remarkable flexure dipping westward, suggesting the presence of a low angle thrust underneath. We found a very low angle fault dipping eastward from an additional 2 m deep excavation. The vertical slip at F1, judged from the height difference with the top of the gravel bed (Bed V), is 12 m. In contrast, faults F2 and F3 to the east of F1 follow the bedding plane of the steeply dipping Uonuma Formation, and are high angle reverse faults with the upthrown side to the east. The vertical slip is 3-4 m for F2 and 7.5 m for F3. Profiling across these faults shows that F1 is clearly expressed as a deformed terrace, but the topographical expression of F2 and F3 is not necessarily obvious. Similar faults to F2 are recognized in the study area from observations of the other three large exposures. We classify the faults in the study area into three types: Type 1 is a blind fault assumed at the base of the eastern limb of the Tokimizu anticline. This fault might be the most important contributor to the formation of the major tectonic relief in the study area, although we have no data to prove the nature of the fault plane itself from this study. F1 fault, demonstrated by Type 2, was found for the first time in this study, and is a low angle reverse fault truncating the structure of the Uonuma Formation with a vertical slip rate of 0.1 m/ka. The Type 3 fault is represented by F2, F3, and F4, and these are interpreted to be flexural slip faults along the bedding plane of the Uonuma Formation. Repeated faulting is confirmed from the progressive deformation of different beds not only for the F1 fault (Type 2) but also for the fold-related secondary faults, F2 and F3. No faulting has occurred since ca. 7,500 years BP, however.
資料
  • 苅谷 愛彦, 佐藤 剛, 小森 次郎
    2008 年 117 巻 3 号 p. 650-660
    発行日: 2008/06/25
    公開日: 2010/05/14
    ジャーナル フリー
     The Kitamatairi River basin has been considered to be a type-location of Pleistocene multiple glaciations of the northern Hida Mountains, central Japan. However, recent geomorphological studies performed in the adjacent area have clarified that the landforms and unconsolidated deposits both of which have been believed to be of glacial origin (i.e., moraines and tills) were deformed or actually formed by landslides. This suggests that both morphogenetic and chronologic reappraisals of landforms and deposits are also necessary in the Kitamatairi River basin. Hence, we measured new radiocarbon ages of unconsolidated deposits in the Kitamatairi River basin (replications for 7 samples from 2 sites and new measurements for 9 samples from 7 sites). All replications showed significant older ages (>20 ky) than previously reported ages. New ages range from late Holocene to late Pleistocene, or before. The chronological concept for landform development in the Kitamatairi River basin should be revised.
2007年度秋季講演会講演報告
  • 石井 武政
    2008 年 117 巻 3 号 p. 661-667
    発行日: 2008/06/25
    公開日: 2010/05/14
    ジャーナル フリー
     The Yellow River is a big river, 5,464 km long, and its basin has a catchment area of 795,000 km2 including a closed inland catchment area. One of the four prehistoric civilizations of the world developed in this basin. Following the Yellow River civilization, most dynasties that ruled major parts of China were located in or around the Yellow River basin. From ancient times the Yellow River has been the mother river of China, as all of the Chinese people agree.
     A five-year project to understand the whole picture of the groundwater of the Yellow River basin was started in 2002, which was called the Yellow River Groundwater Project. This was part of a larger project called Research Revolution 2002 (RR2002) under the auspices of the Ministry of Education, Culture, Sports, Science and Technology, Japan. As the Yellow River basin was a major research field, research activities were carried out with close cooperation among Geological Survey of Japan and China Geological Survey, and several universities and related institutions of the two countries.
     The Yellow river basin extends in EW and the difference in elevation between headwater and river mouth is about 5,000 m. At the headwater there are small glaciers and permafrost areas. In the Yellow River Groundwater Project, surveys and observations of permafrost were carried out at the headwater area. Hydrologic surveys of groundwater and surface water were conducted throughout the basin, and collected water samples were analyzed for general quality and oxygen and hydrogen isotope ratio. As knowledge of rocks and formations containing groundwater is very important, information concerning geology, especially the thickness of aquifers and locations of faults was carefully examined.
     The final target of the project was reconstruction of past groundwater by developing a groundwater circulation model of the vast Yellow River basin, taking account of all data collected, and predicting the future from the model thus constructed. The model we developed is a three-dimensional groundwater circulation model covering an area of about 1.6 million km2. Simulation results, for example on the North China Plain, show an extreme lowering of the deep groundwater head after twenty years if groundwater is extracted with the same pumping trend as at present.
地学クラブ講演報告
  • 兼岡 一郎
    2008 年 117 巻 3 号 p. 668-673
    発行日: 2008/06/25
    公開日: 2010/05/14
    ジャーナル フリー
     Based on radiogenic isotopes, we can obtain information about the Earth related to time. Radiometric dating is a typical example. Due to the advanced development of current analytical techniques, radiometric ages covering the Earth's entire history can be obtained with an error of less than 1%, even for a mineral crystal. However, there still remain problems to be clarified including the reliability of decay constants and the meanings of value obtained.
     In another approach, an isotope ratio including a radiogenic isotope can be used to clarify the evolution of the Earth. By applying multiple isotope systematics for typical volcanic rocks such as Mid-oceanic ridge basalts (MORBs) and oceanic island basalts (OIBs), we conjecture the chemical state of the Earth's interior such as the degree of chemical fractionation and degassing. As an additional material used for clarifying the Earth's deep interior, I demonstrate the significance of kimberlites which might reflect the state of the Earth's deep interior more directly than OIBs.
  • 石原 舜三
    2008 年 117 巻 3 号 p. 674-677
    発行日: 2008/06/25
    公開日: 2010/05/14
    ジャーナル フリー
     Worldwide, HREEs are not abundant, but LREEs are. HREEs are limited to certain weathered crust deposits in China where the original granites are rich in HREEs and surface weathering is intense. Because of environmental limitations on mining, it is necessary to discover the primary sources of REEs in alkaline igneous rock provinces. Indium can be recycled easily, and primary sources can be found in Sn-Zn-sulfides deposits of both volcanic and subvolcanic settings. Tungsten and bismuth are also limited mineral resources, but can be found in carbonate rocks with fractionated ilmenite-series granite intrusions. Molybdenum can be supplied sufficiently from porphyry-type deposits.
東京地学協会第11回海外巡検報告
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