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Volume 51, Issue 1
Displaying 1-8 of 8 articles from this issue
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Chiba Okanezawa Active Fault Survey Group1997 Volume 51 Issue 1 Pages 1-4
Published: 1997
Released on J-STAGE: July 11, 2017
JOURNAL OPEN ACCESSDownload PDF (2464K) -
Yasumoto SuzukiArticle type: Article
1997 Volume 51 Issue 1 Pages 5-7
Published: January 25, 1997
Released on J-STAGE: July 11, 2017
JOURNAL OPEN ACCESSThe levelling and triangulation surveys for several tens years show that the mountains upheave and the plains subside steadily and the shear strains are accumulated around the mountains where most of the destructive earthquakes have occurred. Many field geologists acquainted with the regional geology should study the levelling and triangulation data in relation to geology in order to predict the destructive earthquakes and to prevent the hazards. Present is the key to the past and geodetic crustal movements give us the key to the figure of dynamic earth.View full abstractDownload PDF (497K) -
Muneki Mitamura, Shusaku YoshikawaArticle type: Article
1997 Volume 51 Issue 1 Pages 8-14
Published: January 25, 1997
Released on J-STAGE: July 11, 2017
JOURNAL OPEN ACCESSThe Osaka sedimentary basin under the Osaka Bay and the Osaka Plain is a tectonic subsidence basin. The Late-Pleistocene and the Holocene sediments are widely distributed in this basin. The Ma13Bed（Holocene marine clay bed）and the Ma12Bed（Late-Pleistocene marine clay bed）are traced precisely and widely through the checks of many bore-hole logs. On the basis of the altitude variation of basal planes of the two beds and local variation of the estimiated sedimentation rates, this basin is divided into at least three tilting basement block areas, namely the Osaka Bay Area, the West Osaka Area, and the East Osaka Area. The maximum sedimentation rates of each block during Late-Pleistocene time are 1.2m/103years in the Osaka Bay Area and 0.3m/103years in the East and West Osaka Area. The maximum rate in the Osaka Bay Area along the Osaka-wan Fault is same as one of the Nobi Tilting Block along the Yoro Fault. The l995 Hyogo-ken Nambu Earthquake was one of the tectonic events between the subsiding block of the Osaka Bay Area and the uplifting block of the Rokko Mountain.View full abstractDownload PDF (893K) -
Hidenori Endo, Yuichi Sugiyama, Shiro Watanabe, Masahiko Makino, Isao ...Article type: Article
1997 Volume 51 Issue 1 Pages 15-28
Published: January 25, 1997
Released on J-STAGE: July 11, 2017
JOURNAL OPEN ACCESSShallow seismic reflection surveys were conducted to reveal the location and the activity of the concealed faults in the central area of the Kanto plain. The profiles indicate the following results. In the Arakawa lowland, the sediment dip is changed, dipping to the northeast in the southwestern side of the boundary, whereas horizontally in the opposite side. The Ayasegawa fault is accompanied by the graven structure probably with some lateral-slip. And at about 1.5km northwest of the Ayasegawa fault, the sediment dip is changed, dipping steeper in the northeastern side of the boundary. In the Nakagawa lowland, faults probably exist in the area extrapolated from the Ayasegawa fault. And near the northeastern boundary of the Nakagawa lowland, faults with graven structure also exist. The distribution of the vertical displacements of the concealed active faults and the shallow subsurface geological structure coincide with the Kanto basin forming movements observed by the level distribution of the Joso Clay bed of the upper Pleistocene.View full abstractDownload PDF (3191K) -
Yutaka Mitani, Shimousa Daichi Research GroupArticle type: Article
1997 Volume 51 Issue 1 Pages 29-39
Published: January 25, 1997
Released on J-STAGE: July 11, 2017
JOURNAL OPEN ACCESSThe northern district of the Shimousa Upland is comprised of several blocks. Movements of these blocks can be recognized in high chronological resolution upon the analyses of distribution in height of the upland and the formations composing it. Most of the boundaries between blocks have been acted since Middle Pleistocene and their relative vertical movements altered their directions frequently. On the boundaries between comparatively large blocks were formed graben-like subsidence zones. The general upheaval movement that have formed these blocks flourished about 50ka before, and probably it continues at present.View full abstractDownload PDF (1837K) -
Mankichi HoriguchiArticle type: Article
1997 Volume 51 Issue 1 Pages 40-50
Published: January 25, 1997
Released on J-STAGE: July 11, 2017
JOURNAL OPEN ACCESSAlong the River Tone crossing the Kanto plain, a lowland topography develops widely. This widely developed lowland was formed by socalled Kanto basin forming movement. Recently, geological observations and studies of surface beds or formations developing on the sites of archaeological excavation on ruins and underground constructions are widely made. As a result, definite regional phenomenon was made clear on the curastal movement and geoenvironment of Holocene, especially the archaeological and historical periods. On the Kazo lowland developing widely on downstreamside of the Middle course lowland of the River Tone, the so-called "burying highland" is sinking ca. 3m among the Kofun period to now a days. And, on the Menuma lowland developing upstream side, was found a earthquake disaster by "Ancent earthquake". namely, eruptive sand and undergraund fissure systems originate in liquefaction of "Ancent earthquake" which happned in the 9th century (818). Recently, this earth quake disaster was found at the southern slope of Akagi mountain situated in the northern part of the Midcourse area of the River Tone. Therefor, "Ancent earthquake" brought out the greater earthquake disasterView full abstractDownload PDF (1933K) -
Satoshi NakanoArticle type: Article
1997 Volume 51 Issue 1 Pages 51-59
Published: January 25, 1997
Released on J-STAGE: July 11, 2017
JOURNAL OPEN ACCESSA pegmatite microperthite from Nango, Otsu City, Shiga, Japan, has been investigated by EPMA mapping in order to clarify calcium distribution. The Nango microperthite (Or77Ab22An1) is a patch or vein type of host orthoclase (Or) and guest albite (Ab). Calcium distribution in the Ab patches is different within a crystal; Ab patches in some areas are relatively enriched in calcium and those in other areas are relatively depleted in calcium. Heterogeneous calcium distribution is commonly observed in almost all the patches. In some patches, calcium is depleted almost completely. These calcium distribution patterns suggest calcium re-arrangement in the Ab patches or removal from them in some stage during cooling, rather than their formation by exsolution. Compositional variations are also found in the Or host.View full abstractDownload PDF (2722K) -
Collaborative Research Group for the Ryoke Belt in the Ikoma MountainsArticle type: Article
1997 Volume 51 Issue 1 Pages 60-71
Published: January 25, 1997
Released on J-STAGE: July 11, 2017
JOURNAL OPEN ACCESSThe Ryoke Belt in the Ikoma-Shigi Mountains, Nara Prefecture, is composed mainly of various kind of Cretaceous granitoids, accompanied by the older mafic rocks and their related Fukihata Quartz diorite. Igneous activities in this area took place in the two district periods, early to middle Jurassic and late Cretaceous. The earlier one commenced with a mafic magmatism, followed by a minor quartz dioritic intrusion. The mafic rocks and Fukihata quartz diorite occur as tectonic blocks by the Cretaceous granitoids. The later one is characterized by the voluminous granitoid intrusions. They are subdivided into the following four phases as follows; 1st phase Shigisan Granodiorite and Takayasuyama Granite 2nd phase Narukawa Granite 3rd phase Katashimo Granodiorite and Katakami Granite 4th phase Minamikawachi Granite and Taike Granite The first phase granitoids are the gneissic granitoids and discordantly intruded by granitoids of the third to fourth phases. The gneissocity of the first phase granitoids is harmonic with the general trend of the metamorphic rocks. The petrographic features of the first phase granitoids indicate that these granitoids are equivalent to the older granitoids in Kinki District. The second phase granitoids are weakly foliatedgranodiorites and widely exposed in the northern part of this area. The second phase granitoids similar to those of the Yagyu Granodiorite. The third phase granitoids are massive and small stock-like granitoids, cross-cutting the general east-west trend of the Ryoke Belt. The fourth phase granitoids are fine-grained and massive, and occur as a small stock or a dyke-like mass which intruded discordantly into the granitoids of the first to third phase. These phase-divisions of the granitoids of this area are mostly correlative with those of the Kinki and Awaji Districts.View full abstractDownload PDF (1502K)
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