著者

小山 真人

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.104, no.1, pp.45-68, 1995-02-25 (Released:2010-11-18)

参考文献数

84

被引用文献数

3 5

---

A multi-disciplinary synthesis was made on the tectonics and seismotectonics in the northwestern Sagami Bay and adjacent areas, where the plate boundary between the Izu-Bonin and Northeast Japan arcs passes and historical M7-8 inter-and intraplate earthquakes frequentlyhave occurred.In a convergent boundary between plates, a displacement between plates is usually accommodatedalong a broad belt of active imbricated thrusts and folds, which develop in a wedge ofan overriding plate. In such a situation, we can easily identify two kinds of plate boundaries: a deformation front and a subduction entrance. The deformation front is a line connecting thethrusts or folds nearest to a trench/trough axis. The subduction entrance is a line connecting theedges of trench/trough filling coarse deposits, which cover a surface of a subducting plate. In Sagami Bay, the deformation front in the overriding Northeast Japan arc is estimated to belocated along the northern and eastern edges of the Sagami Basin, while the subductionentrance of the subducting Izu-Bonin arc is estimated to be located along the southern edge of the Basin.Many geomorphological, geological, geophysical observations need and support the existenceof the West Sagami Bay Fracture (WSBF), an intraplate propagating fracture between the Izu-Bonin outer and inner arcs, proposed by Ishibashi (1988), whereas these observations require slightmodification of the estimated geometry around the WSBF. Frequent dike intrusions in theHigashi Izu monogenetic volcano field cause spreading of the upper crust and probably move the Manazuru “microplate”(MNZ) to the NNE direction against the Izu block. The Tanna-Hirayama tectonic line is proposed as a transform fault, which accomodates the relativemovement between the MNZ and the Izu block. In the MNZ hypothesis, the Kozu-Matsuda fault, located to the northeast of the Izu Peninsula, is interpreted as a deformation front between theoverriding Northeast Japan arc and the MNZ, which is buoyantly subducting beneath the Oiso Hilland Tanzawa Mountains. The proposed new geometry around the WSBF and the hypothesis of the MNZ can explain (1) the crustal structure and tectonic features around the Kozu-Matsudafault, (2) tectonic implication of the “Oiso-type” earthquakes, which are expected to displacethe Kozu-Matsuda fault periodically, and (3) the rapid upheaval of the Tanzawa Mountains since 1Ma.

著者

矢島 道子

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.114, no.4, pp.609-613, 2005-12-25 (Released:2009-11-12)

参考文献数

6

著者

花輪 公雄

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.114, no.3, pp.485-495, 2005-12-25 (Released:2009-11-12)

参考文献数

12

---

The oceans play important roles in the formation of the earth's climate, and in climatic variations and change. One of these important roles is meridional heat transport due to oceanic general circulation, especially three-dimensional thermohaline circulation through the entire water column. The oceans transport a huge amount of heat-as much as that of the atmosphere. Accordingly, the north-south gradient of surface air temperature is greatly mitigated. Corresponding to global warming due to increases of greenhouse gasses, the oceanic heat content hasincreased sharply. Global warming might cause a weakening of the strength of thermohaline circulation.

著者

亀倉 正博

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.112, no.2, pp.262-276, 2003-04-25 (Released:2009-11-12)

参考文献数

82

被引用文献数

1 1

---

Extreme halophiles (halobacteria) are microorganisms that require a high concentration of NaCl for their optimal growth. They belong to the domain Archaea, together with methanogens and some thermophiles. It has been shown that halobacterial cells are entrapped within the fluid inclusions when NaCl crystallizes, and viable cells could be recovered after many months. Many halobacteria have been isolated from Permian halite, however, few studies are generally accepted due to questions about sample quality and contamination.A recent report that a halophilic bacterium was isolated from a fluid inclusion within a primary salt crystal of the Permian (250 Ma) suggested again that previously reported isolations of halobacteria from Permian halite might be true. The requirement for elevated salt concentration, the probable ability to survive within low water activity environments for long period, and the presence of concentrated KCl in the cells, which is shown to protect DNA and proteins from harmful irradiation, makes halobacteria likely candidates for life on early Mars.

著者

後閑 文之助

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.88, no.2, pp.63-87, 1979-04-25 (Released:2009-11-12)

---

Japanese historical and geographical literatures, the Kojiki, the Nihongi, the Fudoki etc., were edited in the 8th century. Studies of minerals, rocks and fossils at that time were done on the basis of the Honzo (Pen-Tsao), Chinese ancient pharmacy. Since the 17th century studies of the Honzo were settled in Japan and progressed independently. With the development of the Japanese industry in the end of the 18th century, the Meibutsu-gaku, or the Bussan-gaku, learning on natural material or product, originated from the Honzo. On the other hand, since the end of the 17th century, Western natural sciences were transmitted to Japan through Dutch Commercial Office in Nagasaki. The eastern sciences such as the Honzo and the Bussan-gaku resulted in the establishment of the modern geology in Japan together with the western sciences.

著者

田口 洋美

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.113, no.2, pp.191-202, 2004

被引用文献数

2 1

---

It is generally assumed that the Japanese society and culture have been developed on the basis of the agriculture, especially on the rice field cultivation. Hunting, therefore, has been considered a sub-culture insignificant in the socio-cultural context as a whole. The author, however, is of the opinion that the two activities, agriculture and hunting, which are seemingly unrelated in outlook, have been strongly linked and have played complementary roles to each other.<BR>Japanese traditional hunters, Matagi, played an important role here as semi-professional hunters, and their hunting has increasingly become market-oriented.<BR>Agricultural activities inevitably destroy the natural habitat of wildlife by reclaiming or clearing forests to make the land suitable for cultivation, thus eliminating wild animals. Ironically, however, crops grown on cultivated land, which are rich in nutrition, attract wild animals. If the farmers intend to keep high productivity, those animals must be efficiently expelled from the man-controlled area. Agriculture is simply incompatible with wild animals.<BR>Hunting for a living, on the other hand, in essentially to capture wild animals, they are either consumed as various resources by the hunter himself or sold or exchanged for the necessities of life. To ensure sustainable hunting, the number of wild animals must also be sustained, which means the number of captures and the reproduction of animals must be well balanced. Hunting activities thus inevitably require coexistence with wildlife.<BR>Hunting and the agriculture, contradiction in principle, however, could and actually have cooperated to form a complementary relationship, which could be called a system : the hunters eliminated wild animals from cultivated land, and the crops attracted game animals for hunting. Around the peripheries of cultivated areas such complementary relationships have been and still are sustained.<BR>Historically, such relationships were gradually established from 17<SUP>th</SUP> to 18<SUP>th</SUP> centuries, when the Edo Shogunate encouraged as its policy to expand agricultural lands. With the technological advances of irrigation systems, marshlands and shoals were turned into rice fields in the plains, and hills and valleys were cultivated in the mountain regions. Hunting then gradually became involved in the agricultural activities to protect farmland from wild animals.<BR>In the later period of the Edo Shogunate, the farmers themselves began to capture or chase wild animals out of farmland. At the same time, some hunters with highly professional hunting techniques began further chasing and hunting game animals beyond the cultivated lands. Villages experiencing greater damage from wild animals often hired such hunters. The resources obtained from the captured animals and birds, such as furs, hides, feathers, tendons, meat, and internal organs and bones for medical use, were supplied to the local markets. Hunting thus found its niche at the peripheries of agriculture and the market that demanded animal resources, though limited in quantities and in the number of consumers the market might have been.<BR>The flow of animal resources, from agricultural land, to the hunters, then to the market, seems to have been established as a system around 18<SUP>th</SUP> to 19<SUP>th</SUP> centuries, as the monetary system began to prevail and currency was widely used.<BR>As Japan turned into the Modern Ages, hunting became more market-oriented and also strictly controlled : hunting was encouraged to supply furs for export to Europe and the US, and for the military use under the Imperial militaristic government at the time.<BR>A historical review of hunting in Japan suggests that, as for the conservation of wildlife, a historical and socio-cultural viewpoint is essential along with ecological and ethological research.

著者

澤田 可洋

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.3, pp.374-394, 2002-06-25 (Released:2009-11-12)

参考文献数

44

被引用文献数

8 7

---

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.

著者

西川 治

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.6, pp.819-836, 1991-12-05 (Released:2009-11-12)

参考文献数

52

被引用文献数

1 1

著者

柳町 治

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.92, no.3, pp.152-172, 1983-06-25 (Released:2009-11-12)

参考文献数

50

被引用文献数

11 7

---

The glacial landforms, consisting of cirques, troughs, moraines, etc., are widely distributed in the vicinity of Mt. Kisokomagatake (2, 956 m) in the northern part of the Kiso Mountain Range. They are obviously classified into the younger and fresh landforms and the older and dissected ones. The older ones are much more extensive than the younger ones. The author discussed the glacial fluctuations and chronology in the drainage basin of Nakagosho-gawa east of Mt. Kisokomagatake, where glacial landforms are well preserved, in order to clarify the developmental period of these two types of glacial landforms (Fig. 1). Geomorphological data (Figs. 2, 11 and 12), geological data (Figs. 3 and 5), sedimentological data (Figs. 710, and Tab. 1) as well as tephrochronological data (Fig. 4 and Tab. 2) were examined to this purpose.Since about 80, 000 years B. P., three stages of glacial advance were revealed in the drainage basin of Nakagosho-gawa. Consequently, they are included in the Last Glacial Age and are named, from older to younger, Nakagoshodani Stadial I, II and III, respectively. Glacial landform development during each stadial were quite different, as described below (Figs. 2 and 13) : 1. Nakagoshodani Stadial I (80, 000-45, 000 years B.P.) This stadial is characterized by the largest extension of glacier. Glacier, attained 100 m or more in maximal thickness, extended from the Senjojiki- and Gokurakudaira- Cirque to the east of Shirabidaira (1, 790-1, 600 m a.s.l.) over a horizontal distance of 2.5 to 3.0 km. Glacial snout was located approximately at 1, 550 m a.s.l.. This glacial advance resulted in the formation of large trough (HG) below the above-mentioned cirques as well as the deposition of till (S-1 gravel bed) at Shirabidaira. The total thickness of till composed of ablation and lodgement till amounted to 50 to 60 m. Besides, lateral moraines were formed at Shirabidaira.2. Nakagoshodani Stadial II (45, 000-30, 000 years B.P.) Though glacier extended to Shirabidaira again, glaciation was limited in extension and magnitude rather than that of the Nakagoshodani Stadial I. Glacier is inferred to have been a maximum thickness of 50 to 70 m. Only the upper part of the trough was further denudated resulting in the formation of relatively small trough (MG) through this glacial advance. Ablation till (S-2 gravel bed), 20 to 30 m in maximum thick, was deposited and formed lateral moraines at Shirabidaira. End and lateral moraines (a, b) were also formed on the thresholds of both the Senjojiki- and Gokurakudaira- Cirque, preceded and accompanied by the retreat of glacier from Shirabidaira.3. Nakagoshodani Stadial III (30, 000-10, 000 years B.P.) Glaciation was much more limited in extension and magnitude than that of the Nakagoshodani Stadial II. The glaciers descending from both the Gokurakudaira-Cirque and the northern half of the Senjojiki-Cirque excavated in the Nakagoshodani Stadial I and II, attained only a maximum thickness of about 20 m. The glacial snouts were at about 2, 290 m a.s.l.. The upper part of the trough, modified during the Nakagoshodani Stadial II, was further slightly denudated resulting in the formation of small trough (LG) through this glacial advance. The formation of lateral moraine (c) in the Senjojiki-Cirque was prior to that of the end and lateral moraines (d-o) in the trough. In the northwestern part of the SenjojikiCirque (A, B), glacier remained up to the latest stage.Judging from the investigation in the drainage basin of Nakagosho-gawa, it can be regarded that the older and younger glacial landforms obviously classified by the degree of dissection are relevant to the Nakagoshodani Stadial I and to Nakagoshodani Stadial III, respectively. Surface area and equilibrium-line altitude of glaciers, the altitude of glacial snouts, etc., during these two stadials are shown in Tab. 3.

著者

棚井 敏雅

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.6, pp.951-966, 1991-12-05 (Released:2009-11-12)

参考文献数

64

被引用文献数

9 11

著者

吉田 明夫 青木 元

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.2, pp.212-221, 2002-04-25 (Released:2009-11-12)

参考文献数

26

被引用文献数

2

---

We show that conspicuous seismic quiescence occurred in large areas along the coast of the Japan Sea before the 1891 Nobi, 1964 Niigata, 1983 Central Japan Sea, and 2000 Western Tottori Prefecture Earthquake. If we had noticed the quiescence that had appeared since the late 1980s along the northern coasts of Shimane, Tottori, and Hyogo Prefectures and had remembered the feature that a large earthquake in the coastal region of the Japan Sea is likely to be preceded by a widely extended seismic quiescence along the coast, we could have paid close attention to the focal region of the Western Tottori Prefecture Earthquake. We think the occurrence of seismic quiescence in a large area before a large earthquake implies that the preparatory process proceeds not only in the focal region, but in the circumferential areas as well.

著者

伊倉 久美子 太田 陽子

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.112, no.3, pp.394-405, 2003-06-25 (Released:2009-11-12)

参考文献数

23

被引用文献数

3 3

---

Well-defined Holocene marine terraces are present continuously along the west coast of the Asahi Mountains. This area faces the Sea of Japan and is located east of the epicenter of the 1964 Niigata earthquake, which caused an uplift with considerable westward tilting of Awashima Island, located west of the epicenter. In contrast, the study area subsided at the time of the destructive 1964 earthquake, although the presence of Holocene and stage 5e or other marine terraces record the long-term uplift during the late Quaternary of this area (Ota, 1971). This paper describes the nature and the age of Holocene terraces, which had not been studied in detail, and discusses the uplift pattern and its tectonic significance.The Holocene marine terrace here is usually wave-cut platform with few beach deposits. At large river mouths, however, there are relatively wide and flat valley bottom plains, burying drowned valleys, and separated by sand dunes from the present beach. Radiocarbon age from the bottom of terrestrial deposits on marine deposits is 6.4 ka or slightly younger, and indicates that the emergence of Holocene terrace took place ca. 6 ka. The former shoreline height of the Holocene terrace ranges from 8 m to 4 m. Thus, the maximum uplift rate reaches 1.3 m/ka, which is larger than the uplift rate deduced from the Ml (stage 5e) terrace. The Holocene terrace is subdivided into two on the southern part of the Budo Mountains, where the uplift rate of Ml terrace is the maximum. The late Quaternary uplift of this area, deduced from marine terraces, is discordant with coseismic subsidence caused by the 1964 Niigata earthquake. This means that the uplift of this study area is not caused by seismogenetic fault for the 1964 earthquake. We cannot find the specific onshore active fault within or at both sides of the Budo Mountains and the Maya Mountains that was responsible for the coastal uplift. To interpret such a long-term uplift of the coastal area, we need to assume that offshore reverse active fault dipping eastward is repeatedly activated. Establishing the exact location, nature, and length of offshore faults is important to interpret the coastal uplift of this area.

著者

志保井 利夫

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.62, no.2, pp.84-94, 1953

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.23, no.7, pp.510a-510a, 1911

著者

小坂 丈予 小沢 竹二郎 松尾 禎士 平林 順一 大隅 多加志

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.94, no.6, pp.551-563, 1985-12-25 (Released:2009-11-12)

被引用文献数

5 5

---

The temperature of fumarolic gas ranged from 100 to 128 °C. These gas usually contained few HCl and SO2, and contained a small amount of H2S. These facts indicated that acidic gas components were absorbed into the aquifer during the cause of ascent. Hot springs may be classified into three types according to their chemical composition : 1) volcanic thermal water type ; 2) sea water type ; and 3) type of mixture of 1 and 2.δD and δ18O of waters collected from this island are high. The rocks from Iwo-jima are all trachy andesite with the SiO2 content of 54-58 %, and with the Na2O+K2O content of 9-10 %.

著者

早川 由紀夫

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.107, no.3, pp.444-457, 1998-06-25 (Released:2009-11-12)

参考文献数

18

---

ハワイ島はハワイ諸島最大の島で, 群馬県と埼玉県を合わせたくらいの面積をもつ。活発に噴火を続けるキラウエアのほか, 歴史時代に噴火記録があるマウナロアとフアラライ, 4,205mの山頂まで車で行くことができるマウナケア, 山頂近くまで深い谷に刻み込まれたコハラ, の5火山からなる火山島である (図1) 。ハワイ・ホットスポットの火山活動を観察するのに最適の島だ。オアフ島のホノルルから直行便が, 東海岸のヒロと西海岸のコナへ毎日数便飛んでいる。私たちはキラウエアに近いヒロへ飛ぶことにしよう。アメリカのレンタカーは一週間単位で借りると割安だから, ハワイ島に7泊する旅行計画を立てるとよい。40ドルの乗り捨て料金を負担すれば, ヒロ空港で借りた車をコナ空港に返すこともできる。実際, 私は11人の仲間といっしょに1997年12月24日にヒロ空港に降り立ち, 南回りで移動して, 12月31日早朝コナ空港から帰国の途についた。この火山見学案内は, そのときの体験と, 過去3回の私自身のハワイ島旅行経験 (1983年, 1987年, 1991年) に基づいて執筆したものである。出発当日に旅行代理店の倒産を知らされるという困難を克服して, 9日間の旅行を実り多く, しかも楽しく終えることができたのは, 旅行に参加した群馬大学教育学部学生と卒業生みなさんの力による。なお, 旅行参加者全員の分担執筆による体験記をウェブページ (http://www.edu.gunma-u.ac.jp/~hayakawa/fieldguide/p/US/HI/hawaii 97.html) で公開している。これから現地に行く人に利用していただけたら幸いです。

著者

西尾 嘉朗 佐野 有司

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.109, no.4, pp.636-645, 2000-08-25 (Released:2010-11-18)

参考文献数

24

被引用文献数

1

---

Based on δ 13C values and CO2/ 3He ratios of North Fiji Back-Arc Basin basalt glasses, wediscuss the carbon geochemical cycle in the subduction zone. Among the North Fiji Back-ArcBasin basalt glasses, there is a close correlation among CO2/ 3He ratios, δ 13C value, and143Nd/ 144Nd ratios. The CO2/ 3He ratios and the δ 13C values of North Fiji Basin basalt maybe attributed to binary mixing between the mantle component (low-CO2/ 3He, high-δ 13C, andhigh-143Nd/ 144Nd) and the subducted (recycled) component (high-δO2/ 3He, low-δ13C, and low-143Nd/ 144Nd). From a simple mass balance calculation, it is derived that the subductedend-member (recycled carbon) has 70% carbonate and 30% organic matter in origin.Assuming that complete decomposition of the subducted organic matters has occurred, most (about 90%) carbonates are not decomposed, because the amounts of subducting carbonatesand organic matters throughout the North Fiji subduction zone are estimated in a ratio of20: 1. This suggests that carbonate can be transported into the mantle through the subduction zones.

著者

新井 智一

出版者

Tokyo Geographical Society

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.114, no.5, pp.767-790, 2005-12-25

参考文献数

47

被引用文献数

2 1

---

This study examines the interaction between the politics in Fussa City and the Yokota Air Force Base, that is "the politics of place, " from a range of political, economic, and cultural processes which maintain the existence of the base.<BR>Military bases are generally established for global geopolitical purposes. However, the establishment of a military base has cultural implications for the local communities where the base is located, i.e., increased concerns about crimes committed by seavicepersons and noise by aircrafts. Although these military bases have some serious impacts, especially in Japan, geographers have not yet examined the issues regarding a particular military base and the resultant politics in the city.<BR>On the contrary, since the 1980s, Anglo-American political geographers have paid more attention to "the politics of place" This refers to the local politics that occur due to the interaction between a structural constraint and the individuality of a particular place.<BR>Therefore, this study examines "the politics of place" on the Yokota Air Base in Fussa City, Tokyo, by using resources from the local newspapers, novels, magazine articles, and council proceedings.<BR>The results are as follows : (1) Owing to the independence between the U.S. Air Force and local political and economic actors, an urban structure and local economy that depended on the Yokota Air Force Base were constructed in Fussa Town after the establishment of the base in 1945; (2) because of this structure, the local economy became to depend on Air Force personnel as consumers; (3) however, due to a shift to the floating exchanging rate and a reduction in the population of the base in the first half of the 1970s, there was a decrease in the influence that Air Force personnel had on the local economy; (4) since the 1980s, an economic agent utilized the "atmosphere" and "image" adjacent to the base to revitalize the local economy; (5) furthermore, the mass media represented Fussa City as a "base town" and conducted a review of the city in the 1960s, thus contributing to its revitalization; (6) during the economic slump in the 1970s, some local political agents were against the existence of the base. However, successive mayors of Fussa City have accepted the existence of the base, and utilized the subsidies it receives from the national government in order to construct the urban infrastructure.

著者

横山 又次郎

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.44, no.2, pp.61-67, 1932

---

更新世中に猿人と今の人類と相異る人類との産した後、その末季に當つて出現した人類がある。之をホモ・サピエンス・フヲッシリスと稚へて、今人の亞種と見倣さるゝ者である。而もそれは一でなく三ある、日ぐオーリニヤック曰くグリマルヂー、曰くクロマニヨンである。中でクロマニヨン種は惜に前の二種より時期上晩生の春である。但し三者其に人類學者の所謂奮石器時代と稽する時期の後半中に隊洲に蔓延してゐた者である。

著者

河角 広

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.79, no.3, pp.115-138, 1970-06-25 (Released:2009-11-12)

被引用文献数

7 13

---

In earlier days most Japanese wanted eagerly to have means of earthquake prediction in order to escape earthquake disaster taking refuge in advance in open spaces since they were almost powerless in encountering the menaces. We are now enabled to long for the mitigation of the disaster by the advancement of science and technology, although we have not yet succeeded to predict the coming of a disastrous earthquake. Our safety thus depend entirely on our effort for the countermeasures against the calamity. But we have only limited allowances for such preparations economically and in time available. It is therefore inevitable to start the preparation from the most important and imminent localities in a country, from the national point of view.In Japan, according to the writer's witness on the imminence of Southern Kwanto District at the Diet in July, 1964, such preparation work for Tokyo Metropolis was started the next month by a new Earthquake Division of the Disaster Prevention Council of the Metropolis, and several important hazard possibilities of the imminent earthquake have been revealed with the result that similar committees have also been made in other prefectures and cities in the same area as well as in the Central Government of the country.In this paper the writer intended to give the ground for his assertion of the imminence of a disastrous earthquake giving proofs of the periodicity of such calamities on the statistical and historical analyses, and made some comments on the possible consequences and major problems in the countermeasures to cope with the conceived disaster as revealed by the studies made on the national and metropolitan levels.In view of the importance, interest and the space allowance, only the proofs of the periodicity in the recurrence of destructive earthquakes in the district concerned are summarised in this abstract.Historical earthquakes in and around Kwanto District as shown in the map (Fig. 2.1) were examined and those which were destructive at Kamakura or presumable as such from the standard intensity-distance-magnitude curve were selected and listed in Table 1.1. Periodicities of these earthquakes were analysed statistically. Similar analyses were also applied to the earthquakes experienced in Tokyo which are listed in Table 2.2. A definite period τ of 69 years (besides a few integral multiples of this period) was clearly found. The methods used in the above analyses were by means of (1) Fourier transforms (Fig. 1.1), (2) autocorrelation functions (Figs. 1.3 and 1.4) and (3) historical examinations of the number of cases when no destructive earthquakes took place within the standard deviation +√ ξ2 from the year tp when a destructive earthquake was expected to occur from the periodicity. Test of persistence of the period was also made by means of the theory of random walks consisting of Fourier amplitudes in successive periods (Figs. 1.5 a and b). Rayleigh-Schuster's criterion (Formula 1.3) that is the probability of obtaining the actual Fourier amplitude on the assumption of no periodicity or the resultant distance of above mentioned random walks gave the values of the probability equal to 0.06% and 0.03% for Kamakura and Tokyo respectively. In comparison to usual value of 5 or 10% for recognizing periodicity in geophysical phenomena, the smallness of the above values is more than enough to disprove the non-existence of the periodicity of 69 years in the recurrence of destructive earthquakes in the districts under consideration.