Journal of Geography (Chigaku Zasshi)
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
Volume 111 , Issue 3
Showing 1-20 articles out of 20 articles from the selected issue
  • Masaru YAMAGUCHI, Yoko OTA
    2002 Volume 111 Issue 3 Pages 323-340
    Published: June 25, 2002
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The east coast of Coastal Range, Taiwan, is well known for the presence of multiple Holocene marine terraces and their very rapid uplift (e.g. Liew et al., 1993). We extended the study area from Hualien to Taitung over a ca. 150-km long coastline. We present some new data on the ages and the heights of Holocene marine terraces and discuss their significance for Holocene coastal tectonics.
    The Holocene marine terrace is subdivided into more than 10 steps at maximum. The highest and oldest terrace, mostly underlain by transgressive deposits, represents the sea level position at the culmination of Holocene sea-level rise and reaches to ca. 80 m above sea level. Transgressive deposits are radiocarbon-dated at several sites, back to ca. 13000 yr BP. The lower terraces are mostly erosional one, overlain by thin coral beds and indicate successive lowering of relative sea-level during the late Holocene. Uplift rate of the coast is very high, ranging from 5 m/ka to 15 m/ka.
    Three tectonic subregions, A, B and C, are identified, based on the pattern of marine terrace features and uplift rate. Subregion A, the northernmost area, is the Milun Upland, which is separated from the main part of Coastal Range by the Hualien River. The Milun Upland is a tilted block, bounded by the active Milun Fault at its western margin, and is fringed by a series of narrow lower terraces. The Milun Fault is a northern extension of the Taitung Longitudinal Valley Fault System and shows progressive deformation. Deformation of the Milun Fault is concordant to that of the 1951 earthquake. Uplift rate here ranges 5-8 m/ka. Subregion B, middle part of the coastal area, has an uplift rate of 5 m/ka. Subregion C is the southern most region, presents multiple terraces characterised by the highest uplift rate, 7-15 m/ka. Extensive alluvial fans overlie most of the highest marine terrace. Multiple lower terraces are also well preserved. The youngest terrace is dated at ca. 400 yr BP. No onshore active fault is observed on terraces in the subregions B and C.
    The presence of many steps during the Holocene time implies that intermittent uplifts, associated with large earthquakes at an interval of one thousand to several hundreds of years, have repeatedly occurred in this coastal area, but with different times and amounts at each subregion. The uplift of subregion A certainly resulted from an onshore active fault (Milun Fault). Causative faults for the uplift of subregions B and C are not identified. Offshore active faults, striking obliquely to the coastline (Lallemand et al., 1999), appear to be causative faults. Another unsolved problem is to understand when such a high uplift started in this coastal area. This is difficult to determine at present, because no late or middle Pleistocene marine terraces are found in the area.
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  • Masafumi OKAWARA, Shinji TSUKAWAKI
    2002 Volume 111 Issue 3 Pages 341-359
    Published: June 25, 2002
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Unique sedimentary processes under the control of drastic seasonal fluctuations in its water level and area are expected in Lake Tonle Sap, the largest lake in Southeast Asia. As a part in a series on pursuing the sedimentary processes and their temporal changes of the lake, sediments and soils were collected and examined from the northern part of the lake and its adjacent water systems and areas in order to reveal composition and provenance of clay minerals distributed in the northern part of the lake.
    Illite, kaolin minerals, smectite and chlorite were commonly identified from the surface and suspended sediments of the lake. Judging from illite and chlorite are not detected in the sediment and soil samples from rivers and the Alluvial plains around the lake but the bottom sediments from the Tonle Sap River that connects the lake with the Mekong River yield a certain amount of them, it is stated that illite and chlorite recognized in the lake sediments were derived from the Mekong River. Since illite and chlorite are not detected in the lower part of the cored sediments from the northern part of the lake in spite of the upper part contains them, appearance of illite and chlorite in the upper part of the core indicates that a change of sediment transport in water systems around the lake took place at about 5, 000 years BP.
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  • Naotatsu SHIKAZONO
    2002 Volume 111 Issue 3 Pages 360-373
    Published: June 25, 2002
    Released: November 12, 2009
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    Previous studies such as that of Meybeck (1987) estimated the CO2 flux from atmosphere to riverwater due to chemical weathering by assuming that the rate of weathering of silicate rocks and carbonate rocks is proportional to the surface areas of rocks (silicate rocks : carbonate rocks = 7 : 3). However, the dissolution rate of carbonates (calcite and dolomite) is in two to four orders of magnitude higher than silicate (feldspar). This may imply that Meybeck's and other previous approaches lead to a large uncertainty in the estimate of CO2 flux. However, their estimates are nearly similar to that of Gaillardet et al. (1999), who estimated the contribution of the weathering of silicates and carbonates to riverwater chemistry based on a large volume of analytical and runoff data of the world's 60 major rivers.
    The thermochemical calculation in the present study indicates that the chemistry of riverwater having a small runoff is controlled by the solubilities of calcite and Na ·Ca-feldspar (Na : Ca = 1 : 1) at atmospheric PCO2 (10 -3.5 atm) and the world-wide average riverwater chemistry plot is close to the Na ·Ca feldspar-calcite-riverwater equilibrium point. This result reasonably explains the similar estimated values of CO2 flux obtained by Meybeck (1987) and others and Gaillardet et al. (1999).
    The conditions for riverwater saturated with Na ·Ca feldspar and calcite were derived based on a dissolution kinetics-fluid flow coupling model and were expressed as functions of τ (residence time of groundwater) and A/M (A : surface area of mineral, M : mass of water).
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  • Yoshihiro SAWADA
    2002 Volume 111 Issue 3 Pages 374-394
    Published: June 25, 2002
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    The detection rate of eruption cloud with Geostationary Meteorological Satellite (GMS ; HIMAWARI in Japanese) is 12.1%, but GMS can detect and track, at a high rate of 81.5%, eruption cloud from a large explosive eruption higher than 10 km which may threaten aviation safety.
    Estimates of the top altitude of eruption clouds within the tropopause based on cloud-top temperature show fairly high values compared to those obtained by ground observations. Growth of vapor clouds over eruption clouds induced by strong ascending currents with eruption-onset may be the reason.
    Apparent dislocation of eruption clouds on GMS images due to the parallax of GMS is clarified for the case of the 1986 Izu-Oshima Eruption, Japan, and the underestimation of cloud-top is possibly due to warming of the cloud-surface by radiation from internal hot material.
    From inspections of the pattern of cloud-extent, type, strength, decay, and duration of eruption activity can be evaluated.
    Differential Thermal Infrared Imagery of GMS-5 is very effective for discriminating ashbearing cloud from ambient atmospheric cloud, but cannot clearly separate an eruption cloud with an extremely high content of water-vapor with phreatic/phreatomagmatic eruption.
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  • Akio YOSHIDA
    2002 Volume 111 Issue 3 Pages 395-403
    Published: June 25, 2002
    Released: November 12, 2009
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    Seismic activity in and around the Japanese islands was conspicuously high in the mid1990s. Further, a number of large earthquakes occurred around the Philippine islands in the early 1990s, and then, around Kalimantan, Sulawesi, Java, and western New Guinea islands. We show that the seisimic activity in the western peripheral region of the Pacific Ocean in 1990s was so remarkable that it contributed substantially to the notable increase of seismic energy released in 1995-1996 worldwide. The activity seems to have started in the region near the Philippine islands. It is improbable, however, that the successive occurrence of large earthquakes in the western peripheral region of the Pacific Ocean was triggered by the impact of one particularly big event such as the 1990 Philippine earthquake or the huge 1991 eruption of Mt. Pinatubo. Instead, we think that the activity might be produced by a slow tectonic event that lasted for a few years and had a spatial scale of several thousands of kilometers.
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  • Mochamad Nugraha KARTADINATA, Mitsuru OKUNO, Toshio NAKAMURA, Tetsuo K ...
    2002 Volume 111 Issue 3 Pages 404-409
    Published: June 25, 2002
    Released: November 12, 2009
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  • Takashi OGUCHI, Helen P. JARVIE, Colin NEAL
    2002 Volume 111 Issue 3 Pages 410-415
    Published: June 25, 2002
    Released: November 12, 2009
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  • Yukinori MATSUKURA, Yukiya TANAKA, Tsuyoshi WAKATSUKI
    2002 Volume 111 Issue 3 Pages 416-425
    Published: June 25, 2002
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    We studied the relations between the lithological properties of bedrock, soil layers, and dimensions of soil slips (depth and slope angle) in slopes on Jurassic granite and Precambrian gneiss in the suburbs of Seoul, Republic of Korea. The slope angle before slippage and the average depth at which slippage initiates are estimated to be about 35-40° and 70-90 cm in granite. The values for gneiss scars are 27-33° and 140-190 cm. Regolith (weathering products) is coarse on slopes underlain by granite and fine on slopes underlain by gneiss, reflecting the grain size of the minerals in the underlying bedrock. Soil layers at the slip (shearing) plane on the granite slope are coarser grained with a larger angle of internal friction (φ) and a smaller cohesion (c) compared to soil layers on the gneiss slope. A slope stability analysis indicates that these properties of soil, themselves derived from weathering, control the difference in dimensions of soil slips found between granite and gneiss.
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  • Kazumi AKIMOTO
    2002 Volume 111 Issue 3 Pages 426-429
    Published: June 25, 2002
    Released: November 12, 2009
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  • Kazunori ARITA, Hiroto OHIRA, Tetsumaru ITAYA, Takaaki MATSUDA, Hideo ...
    2002 Volume 111 Issue 3 Pages 430-435
    Published: June 25, 2002
    Released: February 25, 2010
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  • Shohei BANNO
    2002 Volume 111 Issue 3 Pages 436-439
    Published: June 25, 2002
    Released: November 12, 2009
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  • Noriyuki IKEYA
    2002 Volume 111 Issue 3 Pages 440-443
    Published: June 25, 2002
    Released: November 12, 2009
    JOURNALS FREE ACCESS
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  • Jun MATSUMOTO
    2002 Volume 111 Issue 3 Pages 444-446
    Published: June 25, 2002
    Released: November 12, 2009
    JOURNALS FREE ACCESS
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  • Tadamichi OBA
    2002 Volume 111 Issue 3 Pages 447-449
    Published: June 25, 2002
    Released: November 12, 2009
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  • [in Japanese], [in Japanese], [in Japanese], [in Japanese]
    2002 Volume 111 Issue 3 Pages 450-455
    Published: June 25, 2002
    Released: November 12, 2009
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  • Katsuyuki KAWAMURA
    2002 Volume 111 Issue 3 Pages 456-464
    Published: June 25, 2002
    Released: November 12, 2009
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  • Junji ITOIGAWA
    2002 Volume 111 Issue 3 Pages 465-469
    Published: June 25, 2002
    Released: November 12, 2009
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  • Motomaro SHIRAO
    2002 Volume 111 Issue 3 Pages Plate1-Plate2
    Published: June 25, 2002
    Released: November 12, 2009
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  • Motomaro SHIRAO
    2002 Volume 111 Issue 3 Pages Plate3-Plate4
    Published: June 25, 2002
    Released: November 12, 2009
    JOURNALS FREE ACCESS
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  • Takashi OGUCHI, Helen P. JARVIE, Colin NEAL
    2002 Volume 111 Issue 3 Pages 410-415
    Published: June 25, 2002
    Released: June 22, 2012
    JOURNALS FREE ACCESS
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