Journal of the Japan Society of Engineering Geology
Online ISSN : 1884-0973
Print ISSN : 0286-7737
ISSN-L : 0286-7737
Volume 41, Issue 6
Displaying 1-8 of 8 articles from this issue
  • Yuji KANAORI
    2001 Volume 41 Issue 6 Pages 323-332
    Published: February 10, 2001
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    Faults are always accompanied by fracture zones, regardless of their dimensions. The characteristics and distribution of fault fracture zones in basement rocks have been extensively clarified, because their existence is taken into account in the site selection and safety design of large structures, such as large dams, underground power stations and nuclear power stations. Recently, materials that constitute fault fracture zones have been investigated and classified as “fault rocks, ” a new category. In field investigations, simple description of “fracture zone” is insufficient. As observations at fault outcrops and optical microscopy can easily distinguish fault rocks, types of fault rocks should be described in detail. Zones influenced by faulting have been found around faults. These zones are called process zones. A process zone is characterized by a greater number of joints, secondary shear fractures and microcracks. It is difficult to know whether or not faulting directly produces all these structures. The existence of a process zone probably influences on the long-term circulation of underground water and diffusion of materials. Characteristics of the process zones should be clarified, in order to facilitate the safe depository of high-level nuclear wastes into geological formations.
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  • Sakae MUKOYAMA
    2001 Volume 41 Issue 6 Pages 333-342
    Published: February 10, 2001
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    The object of active fault investigation is long term prediction of destructive earthquakes. Its result shall give important information for earthquake disaster mitigation. And information is useful to social decision and social agreement to encourage risk mitigation in vulnerable communities. Therefore, reliability of the result is important. However, there are little well trained specialists in government, so it is difficult to make common understanding on the uncertainties of the results of investigation. Moreover, the process of the investigation is complicate and reliability of finding is not precise. Therefore, it is necessary to mention strictly on the reports about the theme, means of solution, remaining problem and uncertainty of the conclusion for each step of survey.
    Additionally, truthful report is not yet up to the mark for actual disaster mitigation. Reliable ommunication between government, specialists, mass media, and citizens, is also very important for effective mitigation of disasters at present.
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  • Present and Future Prospect
    Toshiaki IKEDA, Hiroaki KUBOTA, Naoto NORIYASU
    2001 Volume 41 Issue 6 Pages 343-350
    Published: February 10, 2001
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    Up to now geotechnical information has been offered by various organizations but often with differing data content and presentation methods, lack of detail in the data and other inconveniences for users. Amid dramatic improvements in the capabilities of information related equipment a unification of the contents and items that geotechnical information should contain is required. At the same time, in design and similar applications an improvement in reliability is required and there is a desire for statistical processing of geotechnical information that includes formation and sedimentation eras.
    In order for such requirements to be met many aspects concerning the data necessary for geotechnical information need to be urgently considered, as the unification of such data is ongoing. Additionally it is desirable to utilize geotechnical information, rather than only for geological surveys and design, and to combine it organically with geographic information. This paper catalogs the problems posed by these requirements.
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  • Some Considerations and Proposals
    Takashi FUJITA, Shuichiro YOKOTA, Akihito NAKASUJI
    2001 Volume 41 Issue 6 Pages 351-362
    Published: February 10, 2001
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    Japan has many steep slopes, and a variety of slope movements (landslides) occur in many places every year. These movements are triggered by heavy rain falls, earthquakes and volcanic activities. As a result, serious disasters with human suffering have occurred. It is difficult to predict the occurrence of such slope movements, and also to prevent or mitigate their hazards.
    Except for some active volcanoes, Japan has few hazard maps for slope movement. This results from such problems of drawing hazard maps as: 1) technical problems for evaluation of slope instability
    2) areas susceptible to debris derived from slope movements
    3) adjustment of a variety of source data
    4) use of digital data for GIS
    5) method of presentation and publication of detailed information regarding hazards from a slope movement
    This paper discusses the importance and contents of hazard maps. Its fundamental studies including analysis of past disaster records, construction of hazard prevention or mitigation system with the cooperation of local governments, research institutes, engineering agencies and inhabitants. We also propose the need to include education and examination for disaster prevention. In 2001, a new law on hazards resulting from slope instability will be enforced. As this law requests a hazard map on slope instability, many useful hazard maps will be published in the near future.
    We show hazard maps on volcanic activity, which are the most excellent ones in Japan, and discuss prediction of volcanic eruption, analysis of volcanic activity, kinds of disaster, analysis of data based on past disasters, method of drawing a hazard map, and the estimation of scenarios of disasters.
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  • -A Case Study in the Yuya Peninsula, Northwestern Yamaguchi Prefecture, Southwest Japan-
    Kiyoshi HISANAGA, Yuji KANAORI
    2001 Volume 41 Issue 6 Pages 363-370
    Published: February 10, 2001
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    A number of landslides occur in the Yuya Peninsula, northwestern Yamaguchi Prefecture. This area contains landslide prevention regions where have designated by the Ministry of Construction or the Ministry of Agriculture, Forestry and Fisheries. Countermeasure projects have been conducted independently by each ministry for their respective regions. Recently, evil for the independence of the countermeasure projects have been evident, because there are differences in the interpretation of landslide mechanisms and the policy of countermeasures among the prevention regions. Macroscopically, these prevention regions are found to have geographical and geological features that are common in the Yuya Peninsula area. In this study, nine landslide prevention regions in this area were selected as case study sites, and the landslides in these regions were analyzed synthetically. This analysis indicated that a number of small landslides at shallow depths originated from a large-scale landslide that occurred in the past. The slipping surface of the large-scale landslide was estimated to be located at a depth of more than 50m in a geological cross section. The small landslides around communities which are located on gentle slopes have been investigated, and countermeasures for small landslides have been taken in each prevention region. However, it is necessary to take into account the large-scale landslide at large depths, in mitigating the natural hazards caused by landslides. Further projects for the prevention of landslides in this area should be planned from a standpoint of macroscopic engineering geology. Those projects must also be free from inter-ministry conflict regarding designation of the regions of landslide management.
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  • Kunio KAWAUCHI, Nobuyuki TAKAHASHI, Kazuo YABE, Shin-ichi URANO
    2001 Volume 41 Issue 6 Pages 371-382
    Published: February 10, 2001
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    We conducted an environmental survey of a wetland using electrical conductivity (EC) measurement and the global positioning system (GPS) in the flood plain of Furen river (43° 17′ N, 145° 15′ E). We used a new portable instrument developed by Kawauchi et al. that can measure apparent EC of different depths. Two electrodes at different intervals (20 and 40 cm) were used to collect data from depths of 20-40 cm. In order to determine the latitude and longitude of measurement sites, differential global positional (DGPS) correction signals within 200 km of a differential beacon operated by the Japan Coast Guard were used. Kushirozaki radio station (42° 58′ N, 144° 23′ E) was used in this survey. We hiked in the wetland carrying an aluminum backpack frame to which a GPS receiver, a DGPS receiver, a mobile computer and a 12-volt battery with a satellite antenna and a 300-kHz DGPS whip antenna were attached and holding a stick to which an earth cable was attached.
    We were able to receive strong DGPS correction signals while sounding the survey. In stationary GPS measurements with DGPS corrections and a good view of the sky, error decreased within an average radius of only 2. 5m due to the lack of the big trees in wetland and due to the cancel on May 2, 2000 of the noise signal (S/A) by the U. S. government. Using our system, we were able to survey an area of 2 km EW x 0. 7 km NS within 2 days. From these measurements, we were able to determine the EC distribution in horizontal and vertical directions of the survey area. EC in the area near the pasture and Furen river was higher than that in the area between them and was highest in the border area of the pasture and river. Most of the trees in the wetland were growing in the areas in which EC was high, mainly near the pasture and road. EC at a depth of 40 cm was higher overall than that at a depth of 20 cm.
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  • Hiroyuki OHNO
    2001 Volume 41 Issue 6 Pages 383-386
    Published: February 10, 2001
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
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  • 2001 Volume 41 Issue 6 Pages 413
    Published: 2001
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
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