Journal of Geography (Chigaku Zasshi)
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
Volume 91 , Issue 4
Showing 1-9 articles out of 9 articles from the selected issue
  • Masaaki KIMURA, Junzo KASAHARA, Seijiro OE
    1982 Volume 91 Issue 4 Pages 217-238
    Published: August 25, 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Spatial and temporal relations between large interplate earthquakes and eruptive activities along Northeast Japan was studied by means of a two-dimensional model using the finite element method. Stress fields were calculated using seismological data in Northeast Japan. The stress value for each earthquake was normalized by using the seismic moment Mo instead of earthquake magnitude M. Stress differences before and after great earthquakes show close relationships with eruptive activities in Northeast Japan. The results suggest that eruptive activities increase under the increased compressive strain of pre-seismic conditions and their activities abruptly decrease under post-seismic conditions.
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  • Shizuo YOSHIDA, Mamoru ADACHI, Shinjiro MIZUTANI
    1982 Volume 91 Issue 4 Pages 239-258
    Published: August 25, 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Tectonic frameworks of the southern Alaska margin and the Outer zone of Southwest Japan were correlated on the basis of geologic structures, lithofacies and geologic ages. Both regions have been situated along the convergent margins of the Kula and Pacific plates since early Mesozoic time and are underlain by several geologic units that are distributed zonally, parallel to each other and younging towards the Pacific side (Fig. 4).
    In the Kodiak Islands-Kenai Peninsula area of the southern Alaska margin, geologic units trend northeasterly and are made up of, from the continental side to the Pacific side, (1) late Triassic to early Jurassic volcaniclastic sequences, (2) early Jurassic Afognak granitic complex and early Jurassic Kodiak-Seldovia schists, (3) early Cretaceous Uyak-McHugh formation consisting mainly of argillite with chert, basalt and sandstone, (4) latest Cretaceous Kodiak-Valdez formation consisting mostly of well-bedded argillaceous turbidites without chert and basalt, (5) Paleocene Ghost rocks formation consisting maingy of argillite and slumped turbidite with minor chert and basalt and (6) Eocene to Miocene shelfslope facies of sandstone and turbidite (Fig. 4, Table 1).
    The Afognak granitic complex and Kodiak-Seldovia schists are lithologically correlatable to the Cretaceous Ryoke complex and Sambagawa schists respectively, but are not clearly separated by a fault like the Median Tectonic Line that separates the Ryoke from the Sambagawa. The Uyak-McHugh formation is lithologically and structurally correlative with the Permo-Triassic Chichibu group, although the former is bounded on the northwest by the Border Ranges fault and the latter is primarily conformable to the Sambagawa schists. In Southwest Japan the Kurosegawa terrane underlain by middle Paleozoic rocks together with older gneisses and acid igneous rocks occupies a narrow zone on the south of the Chichibu group, whereas no such terrane with continental crust occurs in the southern Alaska margin. In addition, no correlative rocks to the Triassic Sambosan terrane consisting mainly of bedded chert and sandstone with subordinate basalt and limestone are present in the southern Alaska margin.
    The Kodiak-Valdez formation corresponds to the Cretaceous Shimanto group in respect of structural position. However, lithofacies and deformation are quite different each other the former consists mostly of well-bedded argillaceous turbidites with ubiquitous and remarkable slaty cleavage, whereas the latter consists mostly of sandy turbidites, commonly chaotic, with subordinate chert and basaltic or rhyolitic volcanics. The Ghost rocks formation corresponds to the Eocene to_ Oligocelle Setogawa group in respect of lithofacies deformation and structural position.
    Major differences of tectonic framework between the southern Alaska margin and the Outer zone of Southwest Japan are ; (1) absence of faultbounded paired metamorphic belts in Alaska, (2) absence of a terrane with thick granitic crust in Alaska, (3) time lags between the correlative units and (4) remarkably shorter depositional durations of individual sedimentary unit in Alaska than those in Southwest Japan (Fig. 4).
    Comparisons between the southern Alaska margin and the Outer zone of Southwest Japan suggest that sedimentary facies, geologic structures and formation process of tectonic frameworks vary significantly even in similar convergent plate margins. Collision mechanisms of continental and oceanic fragments (e. g. JONES et al., 1972 ; CONEY et al., 1980 ; BENAVRA-HAM et al., 1981); which are valid in the west coast of North America, should be examined in Southwest Japan as well.
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  • Iwao TATEIWA
    1982 Volume 91 Issue 4 Pages 259-272
    Published: August 25, 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    Geological researches of the Philippine Basin have been greatly advanced by works on the islands of frontal arc systems, by deep sea drillings, and by marine geophysical surveys. However, we cannot constract any concrete concept on the basin genesis. We can only suggest some speculative and qualitative indications arising from the synthesis of data, as follows.
    1 : Since the Middle Eocene or in places since the Oligocene or Early Miocene, the Philippine Basin has been almost entirely under sea, where thick beds of limestone and miscellaneous elastics often rich in fossils, together with volcanic ash, volcanic conglomerates and breccias, and volcanic rocks mostly basic in character were formed.
    2 : Synthesis of these data also suggests that the basin was subjected to wide spread crustal movements at least three times, namely the age ranging probably from the Late Cretaceous to the Early Eocene, the Mid-Tertiary and lastly the Pleistocene, and that the fundamental features of the submarine physiography as shown in the basin at present were formed most probably in an early stage of the Eocene.
    3 : It has been announced that the Daito Ridges area is constructed of continental crust (MIZUNO, 1975), extent of which, however, remained almost unexplained. In the writer's conception, areas extending widely from the Izu-Hakone crustal block in Central Honshu, Japan, so far as Izu Is. and adjacent areas of Yap Is., Palao Is., Halmahera Is. and Vogelkopf Penninsula of New Guinea are also constructed almost no doubt of continental crust. It may be rather possible that the basin is constructed entirely of continental crust, and further that the continental crust had been long remained in a state of continental land until it was covered by the Tertiary marine water.
    4 : The characteristic physiographic pattern shown by the NW-SE parallel arrangement of Daito Ridges, Shikoku Basin, Kinan Sea-mounts Area together with the Izu-Mariana insular arc-trench system is in fact note-worthy feature in the northern part of the Philippine Basin, the arrangement being nearly perpendicular in direction against the arcuate structure of the frontal insular arc-trench system of East Asia in the Angara Land. The characteristic feature may strongly suggests that the Philippine Basin belongs to a global structural unit, quite different from the Angara Land, and that the basin crust is most probably covered by the overthrusted plane of the East Asiatic frontal belt drifting away from the continental Angala Land.
    5 : In structure, the Philippine Basin extends southeasterly so far as New Zealand area as shown in Fig. 2, sarrounding Austrarian continent of the Gondwana Land, and constructing a frontal tectonic zone of the Gondwana. The tectonic zone is appropriately called the Austro-Philippine Tectonic Zone by the present writer, the tectonic zone being comparable in structural development with the Northwest Pacific Tectonic Zone (TATEIWA, 1976, 1979) of the Angara Land.
    6 : It is percieved that the Mariana trough has been extended at rates up to 10cm/yr. or more during the last 2-3 m. y. (KARIG, 1973). In general concept, however, these phenomena may be a matter of naturally expect in considering the genetic relationships between arcuate structure of insular arcs and inside marginal sea. Hypothetical setting of sea-floor spreading axis, specially fixed, for elucidation of the phenomena, seems to have no convincing basis.
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  • Shosuke Hosoi
    1982 Volume 91 Issue 4 Pages 273-284
    Published: August 25, 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
    In Venezuela, National Inventory of Lands has been carried out since 1968 by COPLANARH, Commission of National Planning of Water Resources and since 1977 by MARNR, Ministry of the Environment and the Renewable Natural Resources.
    The results of the inventory have been published in reports with maps of geomorphology, soils, land use, morphodynamic balance, land use capabilities (in the three systems : 1-natural, 2-with drainage, and 3-with drainage and irrigation) mostly at a scale of 1 : 250, 000. This inventory has covered about 321, 500 km2 by the end of 1980. The contents of the inventory is described briefly in this paper. Other surveys related to land resources are also mentionned briefly.
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  • Teiichi KOBAYASHI
    1982 Volume 91 Issue 4 Pages 285-291
    Published: August 25, 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
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  • [in Japanese]
    1982 Volume 91 Issue 4 Pages 292-293
    Published: August 25, 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
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  • [in Japanese]
    1982 Volume 91 Issue 4 Pages 294
    Published: August 25, 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
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  • 1982 Volume 91 Issue 4 Pages e1
    Published: 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
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  • M. ADACHI
    1982 Volume 91 Issue 4 Pages Plate1-Plate2
    Published: August 25, 1982
    Released: November 12, 2009
    JOURNALS FREE ACCESS
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