著者

岡田 義光

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.3-4, pp.307-308, 2007-08-25 (Released:2009-11-12)

著者

池内 幸司 伊藤 夏生

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.3-4, pp.490-503, 2007-08-25 (Released:2009-11-12)

参考文献数

8

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The Central Disaster Management Council conducted damage estimation research on the next Tokyo Metropolitan Earthquake. The estimation clarified that the earthquake would bring not only a huge amount of physical damage, but also serious influence on the metropolitan functions such as politics, administration, and economy. The “Policy Framework for Tokyo Metropolitan Earthquakes” was set to secure the continuity of metropolitan functions as well to reduce damage. The “Tokyo Metropolitan Earthquake Disaster Reduction Strategy” was also shown by setting quantitative disaster reduction objectives with definite deadlines and concrete plans to execute disaster reduction measures effectively and properly. Furthermore, the “Guidelines for Tokyo Metropolitan Earthquakes Emergency Response Plan”, which provides the contents of emergency activities in a large area, and procedures and roles of government in the event of a disaster, was regulated. Measures for evacuees and people stranded without bearable means of returning to their homes, and contingency plans for central governments are under discussion.

著者

江口 孝雄 堀 貞喜

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.3-4, pp.325-369, 2007-08-25 (Released:2009-11-12)

参考文献数

142

被引用文献数

1

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We present a new view of the morphology of slab (s) subducted just beneath the Tokyo Metropolitan Area in Japan. Previously, several different models of the surface geometry of the subducted Philippine sea plate slab (PH slab) have been published mainly using seismicity data (e.g., Nakamura and Shimazaki, 1981; Maki, 1984; Kasahara, 1985; Ishida, 1992; Noguchi, 1998; Hori, 2006).In this study, first we discriminate a previously unknown seismic slab (called slab SG, or seismic slab SG) above the downgoing Pacific plate slab (PC slab), second identify the possible internal structure of slab SG, and third demonstrate tectonic evolution models. It is clear that the currently known surface contours of PH slab indicate the shallowest part of slab SG as well.Most previous studies assumed a PH slab with a constant thickness, and paid little attention to the tectonic characteristics of the vertical extent and/or the bottom geometry of slab SG with variable thickness. The bottom extent of the seismic slab SG beneath the Metropolitan area reaches 36.5N at least. The horizontal extent of seismic slab SG covers most of the lowland Kanto Plain. The bottom depth of slab SG is approximately 120 km near 36.5N and 139.0E, being the same as the surface depth of the PC slab there. Below the Sagami Trough axis near 34.5N and 140.0E, the lowest portion of slab SG is located at a depth of 80 to 90 km. The western bottom end zone of slab SG generally strikes in the NNW-SSE direction, being approximately parallel to the volcanic front.We suggest four basic morphology models of slab SG as follows. (1) Slab SG consists of both the PH slab at a shallower depth and a deeper underlain slab (slab SL). (2) A bookshelf-like configuration of northwardly inclined multi-slabs on the PC slab due to the intermittent southward shift of accumulation sites of short slab tips with episodic subduction at just south of the previously active paleo-Sagami Trough (s). We emphasize that the above evolutional bookshelf model is, to some extent, similar to the sediment layer accretion process near the deep trench system, but the dynamic situation is not the same. (3) A structure combining models (1) and (2). (4) Slab SG is merely the eastern part, having been cooled by the downgoing PC slab, of 65-70 km thick lithosphere of the Izu Outer Block (JOB) without any other slab components.To clarify the structure of the SG slab in more detail, we should incorporate high-gain seismic data from the on-line operating dense seismic observation network deployed at both marine and land areas covering the metropolitan area. In addition, we must study the effects of 3D mantle wedge circulation with dehydration process due to the subduction of both PC and PH slabs from different directions, as well as the space-time evolution history of accretion tectonics at the northern end zone of the Philippine sea plate.

著者

瀬野 徹三

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.3-4, pp.370-379, 2007-08-25 (Released:2009-11-12)

参考文献数

27

被引用文献数

2 2

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I discuss the danger of earthquakes occurring directly beneath the metropolitan area from temporal and geographical viewpoints. Temporally, large (M>7) earthquakes in Kanto occur 70 years before and a few years after great interplate Kanto earthquakes. The recurrence times of such great earthquakes are more than 220 years. Because 80 years have passed since the last one, at least60 years remain before reaching the active period. It is not legitimate to calculate the probability of large earthquakes occurring in the near future, using the rate of occurrence during the active period before a great earthquake. From a geographical viewpoint, S. Kanto is located in the outer zone south of the Median Tectonic Line, where few active faults are distributed. However, in S. Kanto, exceptionally, the Tachikawa fault and the 1855 Ansei-Edo earthquake are located in the outer zone. This zone is specified by a low-velocity zone in the mantle wedge of the upper plate. Dehydration from the subducting slab may weaken the upper plate in this zone, producing anomalous intraplate earthquakes. The upper crust above this low-velocity area should be marked especially as an area having a potential for large earthquakes in the future. The probability of M7 earthquakes being generated at the interface between the Philippine Sea and the upper plates is small. Temporally, the danger of large earthquakes occurring in the near future beneath the metropolitan area does not seem to be large.

著者

米地 文夫

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.97, no.4, pp.317-325, 1988

被引用文献数

5 2

著者

橋本 徹夫 菊地 正幸

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.1, pp.118-125, 2002-02-25 (Released:2009-11-12)

参考文献数

17

被引用文献数

1 1

---

Subevents of the 1946 Nankai earthquake (Mjma8.0) were distinguished from seismograms recorded on smoked papers with strong motion seismograms (T0=6s, amplification=2) and seismological data of Japan Meteorological Agency. Location and origin time of each subevent were roughly estimated from a hypocenter determination with phase readings of P and S waves for the subevent. Rupture of the Nankai earthquake started at a point southward about 50km off Cape Shionomisaki (first subevent). The rupture propagated in the NNW direction with a rupture velocity of 1.9 km/s and a second subevent that grew to class M8 started after about 16 sec from the initiation of the first subevent. Then the rupture propagated westward, and third subevent of M8 occurred around Tosa Bay, located about 200 km from the second event, about 53 sec after the initiation of the second event. Seismic waves were excited near Tosa Bay during the 1946 Nankai earthquake.

著者

橋本 亘

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.74, no.6, pp.295-316, 1965-12-25 (Released:2009-11-12)

参考文献数

159

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.21, no.10, pp.723b-724, 1909

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.31, no.2, pp.143a-144, 1919

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.10, no.12, pp.691a-691a, 1898-12-22 (Released:2010-12-22)

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.47, no.1, pp.50a-50a, 1935-01-15 (Released:2010-12-22)

著者

宮部 直巳

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.60, no.2, pp.53-56, 1951-06-30 (Released:2009-11-12)

参考文献数

7

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Herewith the crustal deformations as revealed by means of precise geodetic surveys are discussed in connection with the crustal deformations revealed as the results of topographical observations, based on the theory of isostasy.With regard to the crustal deformations found by geodetic methods, it is pointed out that the acute crustal deformations which might have accompanied the destructive earthquake is seen as occurred in reverse direction against the pre- or post-seismic chronic crustal deformations.It is also pointed out that the mode of the acute crustal deformations is such that the earth's crust rises where the gravitational anomalies are positive and vice versa, and that the mode of crustal deformations found as the results of topographical observations seems to agree with that of the acute crustal deformations.

著者

山下 傳吉

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.10, no.2, pp.83-86, 1898-02-20 (Released:2010-10-13)

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.27, no.7, pp.619-621, 1915-07-15 (Released:2010-12-22)

著者

福岡 義隆

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.2, pp.119-124, 1993-04-25 (Released:2010-11-18)

参考文献数

18

被引用文献数

1 1

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Informations on the cold weather and climatic disasters during part of the Little Ice Age for 17th to 18th Century in Japan were obtained from tree ring widths and some kinds of historical documents.Tree rings were analyzed both at Northeastern Japan (Fukushima Pref.) and Southwestern Japan (Okayama Pref.) mostly in Shinto Shrines' precincts. The daily weather records described in old personal documents such as diaries were inquired into at Hirosaki City (Aomori Pref.) for Fukushima's tree rings and at Tsuyama City (Okayama Pref.) for Okayama's tree rings. In this study, the snowy days' rate is used as an indicator of winter coldness. It is defined as the percentage of the number of days with snowfall to that with precipitation, that is, the total of rainy and snowy days.As a result, it could be concluded that the tree ring widths are narrower in the year of larger snowy days' rate. In Southwestern Japan, it is also considered that the drought summer as well as coldest winter caused the worse growth of trees.

著者

磯崎 行雄 丸山 茂徳

出版者

学術雑誌目次速報データベース由来

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.5, pp.697-761, 1991

被引用文献数

77 206

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The Japanese Islands consist fundamentally of late Paleozoic to Cenozoic accretionary complexes that formed in situ in a subduction zone along the East Asian continental margin, i.e. 2.0 Ga Yangtze craton (South China) and 450 Ma fore-arc ophiolite. Recent research utilizing microfossil and radiometric dating has distinguished several major accretionary complexes, including high-P/T metamorphosed parts, and subordinate ophiolites. In particular, recognition of oceanic plate stratigraphy and age of subduction-related metamorphism for individual accretionary complex allows the geotectonic subdivision of the Japanese Islands be emended with a new definition of geotectonic units and their mutual boundaries. Removing the effect of arcrelated magmatism and secondary tectonic modification by microplate activities such as backarc basin opening, fore-arc sliver movement, and arc-collision, a remarkable oceanward younging polarity is recognized among the accretionary complexes. This polarity in growth is well observed in Southwest Japan where seven distinct units occur, i.e. from the Japan Sea side to the Pacific side: 400-300 Ma high-P/T schists, Permian (250 Ma) accretionary complex, 230-180 Ma high-P/T schists, Jurassic (180-140 Ma) accretionary complex, 100 Ma high-P/T schists, Late Cretaceous (80 Ma) accretionary complex, and Tertiary (50-20 Ma) accretionary complex. The sinuous surface trajectories of these geotectonic boundaries and occurrence of several tectonic outliers and windows indicate that all these complexes, including high-P/T schists, occur as subhorizontal (or gently northward dipping) thin tectonic unit, i. e. nappe. Thus the Japanese Islands form a huge pile of nappes that become younger structurally downward to the modern Nankai accretionary complex. What is remarkable in this subhorizontal orogen is that high-P/T units are tectonically intercalated between low-P units, e. g. the thin nappe of 100 Ma Sanbagawa blueschists between Jurassic and Late Cretaceous accretionary complexes of the prehnite-pumpellyite facies. Uplift of the Sanbagawa high-P/T unit appears to correlate with the arrival of the Kula/Pacific spreading ridge at the trench, suggesting that this high-P/T accretionary complex may have been extruded and uplifted into low-P domain in fore-arc by buoyant subduction of the spreading ridge at the trench. Evidence of ridge subduction at that time is supported by reconstructed paleoplate motion and the coeval climax of arc-related Ry-oke magmatism associated with low-P/T regional metamorphism. Formation of older high-P/T blueschist nappes sandwiched between low-P units can be explained likewise. Subduction of major spreading ridges seems most critical for the episodic oceanward development not only of subhorizontal high-P/T nappes but also of continent side granitic belts.

著者

田中館 秀三

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.38, no.7, pp.374-390, 1926-07-15 (Released:2010-10-13)

被引用文献数

3

著者

田中館 秀三

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.38, no.3, pp.130-135, 1926-03-15 (Released:2010-10-13)

被引用文献数

1

著者

田中舘 秀三

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.38, no.4, pp.188-201, 1926-04-15 (Released:2010-10-13)

被引用文献数

1

著者

田中舘 秀三

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.38, no.6, pp.324-329, 1926-06-15 (Released:2010-10-13)