著者
早川 由紀夫 由井 将雄
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.28, no.1, pp.1-17, 1989-05-31 (Released:2009-08-21)
参考文献数
23
被引用文献数
22 14

The eruptive history of the Kusatsu Shirane volcano is well described by means of 14 beds of key tephra and intercalating loess soil. Three eruptive stages are recognized. During early or middle Pleistocene the Matsuozawa volcano was formed; this is the first stage. The second stage was initiated by effusion of the Horaguchi lava, which was followed by eruptions of the Oshi pyroclastic flow, older lava flows, 3P pumice fall, and Yazawahara pyroclastic flow. Brown loess soil about 10m thick covering these deposits indicates that a dormant period of more than 100, 000 years followed this stage. The summit area upheaved about 400m or more against the foot of the volcano during this period, as is suggested by the extraordinarily steep (6.1°-3.0°) surface of the Oshi ignimbrite plateau. The third stage, which started about 14, 000 years ago, is the formation of three pyroclastic cones on the summit and contemporaneous effusion of the younger lava flows, e. g. the Kagusa lava of 7, 000 years ago and the Sessyo lava of 3, 000 years ago. In historic times, phreatic explosions have frequently occurred on the summit crater, Yugama. This means that the present belongs to the third stage. It is unlikely that eruptions of the third stage are caused by cooling of the magma chamber which was active in the second stage. The activity of the third stage seems to denote arrival of a new magma chamber at shallow depth.
著者
山崎 晴雄
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.16, no.4, pp.231-246, 1978-02-28 (Released:2009-08-21)
参考文献数
32
被引用文献数
14 6

The Musashino Upland, a dissected fan of the Tama River in the western suburbs of Tokyo, is displaced by the Tachikawa fault, which runs in a NW-SE direction with long-continued flexure scarps.Using the tephrochronological method and data of water well logs, the author investigated geomorphic features and movement history of the fault in detail. It is thus revealed that the fault has displaced the terrace surfaces of various ages, including the Tc3 surface of 14, 000 years B.P. and the Holocene old stream channels (Fig. 1, Fig. 10). The Plio-Pleistocene sediments, buried under the Musashino Upland, have been vertically displaced about 70m at Hakonegasaki (Fig. 5, Fig. 6). This fault has only vertical displacement with no strike-slip component, and the upthrown side of the fault is northest. The long-term average slip-rate, derived from the displacement of terrace surfaces, is the largest in the central part of the fault and gradually decreases toward the both ends. The maximum average slip-rate is 36cm/1000 years.The total length of the fault is 21km. If examined in detail, it may be divided into two segments from discontinuity of the geomorphic expression and difference in the long-term slip-rate (Fig. 11). No sign of fault movement has been found from precise levelling across this fault for 40 years. So it is thought that fault movements had been recurred on this fault with large earthquakes in the late Quaternary period. The fault displacement in an earthquake, the earthquake magnitude, and its recurrence interval are estimated at about 1.8m, M. 7.1, and 5, 000 years, respectively.There are two types of surface deformations along the Tachikawa fault. One is a flexure scarp of 100-300 meters in width (Fig. 8). This flexure scarp is thought to have been formed by the existence of thick unconsolidated fluvial gravel deposits overlying the faulted Plio-Pleistocene sediments. The other is a broad undulation of a few kilometers in a half-wave length across the fault trace (Fig. 12). This undulation seems to reflect the elastic dislocation of the crust due to the movements of the Tachikawa fault.
著者
早川 由紀夫
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.30, no.5, pp.391-398, 1991-12-25 (Released:2009-08-21)
参考文献数
24
被引用文献数
11 5

Tephra provide extremely useful sedimentary beds for Quaternary research because they are highly reliable time markers. Tephra studies in Japan have advanced primarily on this basis. Because tephra themselves are products of volcanic eruptions it is quite possible to study explosive eruptions using tephra beds. The thickness of the beds tells us the magnitude of the eruption, while the dispersal pattern of the tephra tells us the intensity of the eruption. The mode of eruption is known by the grain-size characteristics of the tephra deposits. The life history of a volcano can be revealed by alternations of tephra and loess beds.
著者
細野 衛 佐瀬 隆
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.28, no.2, pp.79-93, 1989-07-31 (Released:2009-08-21)
参考文献数
42
被引用文献数
2 1

The old burial mound“Komatsu Kofun, ”which has been buried under the River Tone alluvial soil, was discovered at Hanyu City in Saitama Prefecture. The bottom of the chamber is situated 3 meters below the surface. It is considered that the mound was sunk by the Kanto Basin-forming movement, and has been buried by river sediments.In this study, the location of Kofun ground was defined by pedological analyses of soil just under the chamber. The following conclusions can be drawn by making a comparison between these data and the characteristics of nearby Kanto loam terraces.1) The basement of the burial mound is Tachikawa loam formation (tephra layer), which was formed in the Late Pleistocene, and Kofun was constructed on Kanto loam terrace. The formation is tephra in situ, not banked.2) As there is no soil horizon A (Kuroboku soil) at the bottom of the chamber, it is estimated that the chamber was set on Tachikawa loam formation, which acquires bearing capacity by stripping coarse structural Kuroboku soil.3) Tachikawa loam formation of the Kofun ground is air-borne and air-laid tephra, and non-tephra particles are also included in it. This mixed-particle tephra is not so extensive as to change the pedological characteristics of the Tachikawa loam formation.
著者
Shigeo SUGIHARA Isao TAKAHARA Mamoru HOSONO
出版者
Japan Association for Quaternary Research
雑誌
The Quaternary Research (Daiyonki-Kenkyu) (ISSN:04182642)
巻号頁・発行日
vol.11, no.1, pp.29-39, 1972-05-25 (Released:2009-08-21)
参考文献数
33
被引用文献数
2 5

This thesis was written of the topography and volcanic ash layers (the so-called Kanto Loam) of the Musashino upland extending over the western region of Tokyo Metropolis. The results are summarized as follows:1) The geomorphic surfaces of the Musashino upland may be divided into Yodobashi, Narimasu, Akabane, Nakadai and Tachikawa terraces from older to younger in order. These terraces are covered with the volcanic ash layers. It was found that the older terraces are covered with the thicker volcanic ash layers, compared with the younger terraces.2) In classifying Yodobashi and Narimasu terraces, two pumice beds, namely SIP and Pm-1 found in the volcanic ash layers are used as key beds. In the case of Akabane and Nakadai terraces, TP would be used as key bed.3) Beneath the sediments of Yodobashi and Akabane terraces, observed are drowned valley features. Those valleys are filled up with marine sediments representing each of the transgression periods. The amounts of transgression are estimated several ten meters with Yodobashi terrace, and several meters with Akabane.
著者
原山 智 大藪 圭一郎 深山 裕永 足立 英彦 宿輪 隆太
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.42, no.3, pp.127-140, 2003-06-01 (Released:2009-08-21)
参考文献数
46
被引用文献数
11 12

飛騨山脈の隆起については,鮮新世後期から更新世初頭(2.7~1.5Ma)にかけて,最初の極大期があったとする点では,多くの研究者の意見が一致している.しかし,その後の第四紀の期間にテクトニックな隆起があったかどうかでは,意見が分かれていた.山麓の堆積物から隆起時期を推定する方法では,山脈の隆起がテクトニックなのか,アイソスタティックなのか,判定困難なため,本研究では飛騨山脈,爺ヶ岳一帯に分布する鮮新世後期~前期更新世の火山岩類の構造を解析した.この結果,これらの火山岩類はコールドロンをなしており,東に70°前後傾動していることが判明した.南方の高瀬川流域や槍穂高連峰での資料を加味すると,前期更新世後半(1.3Ma~)以降,飛騨山脈東半部の広い範囲で,東西圧縮場のもとでの挫屈による傾動・隆起を生じていることが明らかとなり,飛騨山脈の2段階にわたるテクトニックな隆起運動が明らかとなった.
著者
埴原 和郎
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.12, no.4, pp.265-269, 1974-02-28 (Released:2009-08-21)

In this paper, the author discussed man's adaptation to the cold and formation of the northern Mongoloids in the light of human adaptability to the climatic conditions.It is widely known that the mammals generally show several adaptations to the climate, among which the most effective factors seem to be the light and the temperature. For instance, in the field of mammalian ecology, the rules proposed by GLOGER, BERGMANN and ALLEN are generally accepted, and they can be also applied on microevolution of the human populations to some extent. Thus, it is said that the Caucasoids have adapted to the cold and moist climate with low radiation of ultraviolet rays, and the Negroids to the environment with high temperature and excessive radiation of ultraviolet rays. In parallel to this, the Mongoloids are regarded as having adapted to the very low temperature and dry weather.However, adaptation in this direction has likely occurred in or just after the latest stage of the Upper Paleolithic, because the Mongoloids from this stage such as the Upper Cave Men show almost no evidence of adaptation to the extremely cold temperature.In this respect, the modern Mongoloids living in the arctic areas may be regarded as the people who acquired their adaptability to the cold in relatively recent stages of evolution. On the other hand, we can find some other populations who retain more or less archaic characters of the Mongoloids in peripheral areas of the Asian and the American Continents, and even in the sub-arctic areas.For instance, the Ainu has so far been attributed their origin to the Caucasian stock. Several recent findings on their blood composition, dermatoglyphics and dental characteristics, however, show close affinity to the Mongoloids.On the other hand, the Ainu still shows unique characteristics in quite rich beard and body hairs, relatively thin subcutaneous fat, partially projected facial bones, etc., and these characteristics do not show high degree of adaptability to the cold climate.On the basis of these fact, it is quite likely that the Ainu might be one of branches of the Mongoloid stock who has less experience to live under the extremely cold environment, and still retains some archaic characters compared with the neighbouring populations. Naturally, this hypothesis should be checked by several other data from the fields of anthropology, prehistory, geology, and other related sciences.
著者
藤井 理行
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.34, no.3, pp.151-156, 1995-08-31 (Released:2009-08-21)
参考文献数
19
被引用文献数
2 2

氷河や氷床の涵養域では,雪とともにさまざまな起源を有する物質が年々堆積している.また雪が氷になる過程では,大気が気泡として取り込まれている.このように,氷河あるいは氷床から掘削により取り出したコアは,過去100~105年の気候や環境変動のタイムカプセルといえ,第四紀研究における分解能のよい情報を提供することになる.雪氷コアの解釈の上で重要なことは,コア年代の合理的な決定である.本論では,季節変化シグナルによる方法,年代示準シグナルによる方法,放射性同位体による絶対年代の決定法,氷の流動モデルによる方法を紹介する.
著者
町田 洋 松島 義章 今永 勇
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.14, no.2, pp.77-89, 1975-06-30 (Released:2009-08-21)
参考文献数
21
被引用文献数
4 6

The tephrochronological study of the eastern foot of Mt. Fuji (Fig. 1) would provide abundant data for analyzing not only eruptive history of Fuji volcano but also other late-Quaternary events, because there lies a large quantity of tephra derived mainly from the volcano. Several marker pumice layers are found sandwiched within great numbers of scoria sheets and are correlated with those in south Kanto, where stratigraphic position and radiometric age of them were well established (Table 1, 2 and Fig. 3). The revised stratigraphy and chronology in this area should play significant role in discussing several Quaternary problems around there.1) Mt. Fuji volcano became active ca. 80, 000 y. B.P., when the most important marker pumice, the Ontake Pm-I, showered. Since then, the eruption of “Older Fuji stage” had occurred more or less continuously until ca. 10, 000 y. B. P. without any significant periods of quiescence. The Older Fuji tephras are estimated at approximately 250km3 in volume, which are distributed extensively in south Kanto (Fig. 6). These explosive activities ended at about 10, 000 y. B. P. and there followed a long quiescent period, succeeded by “Younger Fuji stage”.2) The fluvial formation formerly called “Suruga Gravels” is a deposit of the ancient Sakawa river ca. 80, 000 y. B. P. The ancient river took its rise in Tanzawa mountains and might have flowed west- or southwestward into Suruga bay, instead of Sagami bay, the present course flows into. The change in river course appears to have taken place during the period from 80, 000 to 60, 000 y. B. P., associated with the growth of the volcanic edifice of Mt. Fuji (Fig. 5).3) The Kannawa fault, one of the most important tectonic lines in central Japan, runs east to west along the northern margin of the area. It branches westwards into two faults; Kn and Ks. Along the Kn fault a thrust is found dipping northward, whereas along most of the course the fault plane is nearly vertical (Fig. 9). The movements of the both faults are younger than the Suruga Gravels, which is displaced vertically more than 50 metres during the last 80, 000 years.
著者
貝塚 爽平
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.1, no.1, pp.22-30, 1957-05-30 (Released:2009-08-21)
参考文献数
15
被引用文献数
4 3

1. 武蔵野台地は, 地形面の連続性と関東ローム層によつて, 下末吉面, 武蔵野面, 立川面およびそれ以下の段丘に大別される. これら各面をつくるものは, 武蔵野面および下末吉面の東京山の手地域にあるものをのぞくと, いづれも礫層であつて, これらの礫層よりなる各面は, 主として多摩川の作つた扇状地である.2. これら各面の縦断面形の比較と武蔵野面の等高線異状の考察から, 武蔵野台地の北部は北東に傾き下る撓曲をうけて変形したことが明らかにされた. この変動は大宮台地には及んでいない. また, 古い地形面ほど大きい変形を示すことから, この運動が継続的なものであることが知られる.3. 洪積世末期には, 武蔵野台地の南部から松戸附近の下総台地に至るほぼ東西の軸を境として, これ以北では関東平野の中心部に向う造盆地運動がありこれ以南では, とくに房総半島北部の地形に著しくあらわれている東京湾の低地を作る沈降運動が行われた.
著者
小野 映介 海津 正倫 鬼頭 剛
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.43, no.4, pp.287-295, 2004-08-01 (Released:2009-08-21)
参考文献数
33
被引用文献数
2 3

完新世後期の濃尾平野における土砂堆積域の変遷について,低地の地形・地質と遺跡の分布や遺物の検出状況をもとに検討した.濃尾平野では縄文時代中期後葉(4,300yrs BP)以降,木曾川扇状地東部を中心に遺跡が分布するようになり,縄文時代後期末(3,000yrs BP)と弥生時代前期末(2,200yrs BP)の2度の画期を経て,西側と南側の地域にその分布域を段階的に拡大させた.各遺跡では,地表面下2m以浅の黒色有機物層やシルトを主体とした細粒堆積物層から遺物が出土しており,遺跡が立地して以降,洪水による堆積物の供給を受けにくい環境が継続したことが推定された.これらから,濃尾平野では完新世後期に木曾川の主流および土砂の堆積域が低地東部から西部へと移行するとともに,堆積環境の安定域が西部や南部へ拡大したことが考えられる.このような変遷過程は,養老断層を境に沈降する西下がりの傾動運動と対応しており,その影響を受けたものと推定される.また,縄文時代晩期(3,000yrs BP)以降における木曾川の顕著な西流傾向と海側の地域における土砂の集中的な堆積は,「弥生の小海退」に相当する海岸線の海側への急速な前進のおもな要因となったと考えられる.
著者
及川 輝樹
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.42, no.3, pp.141-156, 2003-06-01 (Released:2009-08-21)
参考文献数
108
被引用文献数
13 14

飛騨山脈の火成活動の消長と,山脈の隆起により生産された礫層の形成時期には,よい同時性が認められる.それは,2.5~1.5Ma(Stage I)と0.8~0Ma(Stage III)における火山活動の増大と周辺堆積盆への礫層の供給の時期であり,その間の1.5~0.8Ma(Stage II)には火山活動が低調で,周辺堆積盆における礫層の堆積が停止している.このことから,飛騨山脈は,激しい火成活動を伴いながら,3Ma以降に2度大きく隆起しているといえる.既知の広域テクトニクスの解析結果と隆起モデルから,各時期の隆起メカニズムを考察する.Stage Iでは伸張から中間応力場下での地殻へのマグマの濃集と地殻の厚化によるアイソスタティックな隆起が考えられる.一方,Stage IIIでは,この地域が圧縮場に変化し,マグマの熱によって弾性的厚さが薄くなった地殻が座屈変形し隆起したモデルが考えられる.このように飛騨山脈は,大規模なマグマの貫入・定置・熱の影響と,伸張から圧縮場への広域テクトニクスの変化とが合わさって形成された山脈といえる.
著者
馬場 悠男
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.37, no.3, pp.259-266, 1998-07-31 (Released:2009-08-21)
参考文献数
31

現代日本人の成立に関しては,明治時代から多くの研究者によって,北方および南方からやってきた複数の起源集団による混血の可能性が示唆され,今日でも広く認められている.すなわち,東アジア全体として,更新世末期(3~1万年前)には南方系と考えられる人々が分布していたが,最近(1万年~5,000年前)は北方系と考えられる人々が急速に拡大した,という理解の上に立って,縄文人は南方系の先住集団であり,弥生人は北方系の渡来集団であって,両者の混血によって現代日本人が成立した,と解釈するものである.このような解釈をまとめたのが埴原和朗の「二重構造モデル」である.その際の,南方および北方からの移動のルートとしては,南西陸橋あるいはその付近の海路が有力であるが,北方のルートの可能性も指摘されている.少なくとも,弥生人の渡来に関しては,九州北部を中心とする地域に集中したことはまちがいない.なお,尾本恵市は,遺伝学的データから,更新世後期にすでに南方系アジア人と北方系アジア人が分化していたと考えている.そうすると,縄文人も北方系の人々に起源を持つことになる.筆者は,化石人類の頭部形態から,縄文人の起源は更新世末期に北東アジア沿岸部に住んでいた人々であると考えている.
著者
小熊 博史
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.35, no.3, pp.219-228, 1996-07-31 (Released:2009-08-21)
参考文献数
37
被引用文献数
1 1

越後平野周辺の旧石器時代および縄文時代の遺跡について,沖積低地の様相を中心に,当時の地形や環境を考慮しながら,立地とその変遷を検討した.越後平野周辺の丘陵を含む全域的な分布と,さらに海岸部を対象にした分布をまとめることによって,遺跡立地と変遷の状況を具体的に明らかにした.その結果,沖積低地への進出の画期は縄文時代前期に求められ,縄文時代後・晩期には分布域が沖積地側に移行する傾向をとらえることができた.また,沖積低地において,縄文時代前期以前の古い遺跡が空白に近い分布を示すことについて,それらの遺跡が越後平野に厚く堆積する沖積層中に埋没している可能性を指摘した.
著者
井上 淳 吉川 周作
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.44, no.5, pp.289-296, 2005-10-01 (Released:2009-08-21)
参考文献数
23
被引用文献数
4 3

琵琶湖西岸に分布する黒色土から採取した黒色植物片について各種分析を行い,微粒炭(高温被熱によって生成した微細な炭)であるかを検討した.その結果,黒色植物片は被熱生成した炭と同様に,反射顕微鏡下で白く輝く特徴,高い反射率,低いH/C比(水素・炭素比)が認められ,黒色植物片は植物の被熱によって生成された微粒炭であると考えられた.また,反射率やH/C比を基に推定された炭化温度から,微粒炭は林野火災や火入れなどの植物燃焼によって生成したと考えられた.土壌中の微粒炭は,AT火山ガラスの多産層位より上位から含まれ,K-Ah火山ガラスの多産層位付近で最も多く含まれていた.こうした微粒炭量の傾向は琵琶湖湖底堆積物でも認められ,琵琶湖湖底堆積物に含まれる微粒炭の発生源の1つとして,琵琶湖周辺の黒色土分布域が考えられる.
著者
鈴木 毅彦 早川 由紀夫
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.29, no.2, pp.105-120, 1990
被引用文献数
15 13

Five distinctive tephra beds (A<sub>1</sub>Pm-A<sub>5</sub>Pm), carrying abundant biotite and quartz crystals, are widely distributed in central Japan. They are here collectively called Omachi APms or APms in short, and are petrographically identified by high refractive indices of hornblende (n<sub>2</sub>=1.685-1.696) and orthopyroxene (γ=1.728-1.737). One bed of the APms is found as far as 239km from the presumed source, Momisawadake in the Hida Mountains, where it is 4cm thick and composed mainly of silt-sized glass. No proximal deposit made up of coarse pumice fragments is found owing to unfavorable preservation of the mountainous landscapes; however, the eruption style is supposed to be of plinian type based on analyses of grain size along the dispersal axis.<br>Assuming that the accumulation rate of loess soil has been constant at each locality, the age of APms is estimated 0.24-0.33 Ma by the overlying soil thickness. Moreover, in the south Kanto district, one of the APms is intercalated between two well-established marker-tephra: GoP (0.25-0.30Ma) and TE-5 (0.35-0.40Ma). It is very likely that the age of APms is 0.30-0.35Ma. The time interval between A<sub>1</sub>Pm and A<sub>5</sub>Pm eruptions is estimated to be less than 0.05Ma, because the thickness of the soil layer intercalatcd between APms does not exceed 106cm at any locality.<br>The Omachi APms are found on the flanks and slopes of many volcanoes in central Japan, such as Azumaya, Yatsugatake, Kusatsu Shirane, and Takahara. They are also found among deposits forming fluvial terraces in north Kanto. The significance of APms as Middle Pleistocene time-markers will be established hereafter.
著者
今村 峯雄
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.40, no.6, pp.509-516, 2001-12-01 (Released:2009-08-21)
参考文献数
15
被引用文献数
4 4

多くの教科書では,弥生時代の開始は300BCとして記されていが,その根拠は必ずしも明確ではない.本稿では,14C年代からみた縄文時代晩期から弥生時代への移行期の絶対年代について考察する.これまで,14C年代測定された縄文時代晩期から弥生時代にかけての遺跡は非常に少なく,そのほとんどが高精度AMS14C測定以前のもので,誤差が大きいこと,しかもそのかなりのデータは資料選択の不適性さ,遺跡の撹乱などの可能性があり,問題が多いことがわかる.これまでの少数の14C年代測定例からみると,縄文時代晩期と弥生時代の画期は750BC~400BCにある.この時期は,14C濃度がほとんど変化しない特異な時期にあたっており,実年代を精度よく求めることが難しい.今後,測定数を集中的に増加させるとともに,年輪試料を用いた14Cウイグル・マッチングなどの高精度測定への取り組みが要請される.
著者
渡辺 満久
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.29, no.3, pp.277-279, 1990-08-20 (Released:2009-08-21)
参考文献数
7
被引用文献数
1 1

Characteristic distributions of shallow crustal earthquakes and active faults can indicate tectonic activity, because both are thought to arise chiefly from tectonic instability.Central Kyushu is the most seismically active region of the island. This active seismogenic region can also be defined as a NE-SW-trending active normal fault zone, which would lead to progressive spreading. On the other hand, northwestern Kyushu, including the Tsushima Strait, is postulated to have a low concentration of strain energy, and a comparatively stable condition is inferred in this region in terms of geomorphic indices and landforms. Thus, the Tsushima Strait region cannot be regarded as a potential tectonically active zone. However, the tectonics of the region are still not understood in detail. Sufficient information on Holocene marine terrace surfaces and on submarine tectonic structures in and around the Tsushima Strait remains to be obtained.
著者
大熊 孝
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.35, no.3, pp.235-246, 1996-07-31 (Released:2009-08-21)
参考文献数
21

河川技術を思想的段階,普遍的段階,手段的段階の3段階に分類し,その観点から越後平野における治水史を松ヶ崎放水路と大河津分水を中心に概観し,それぞれの技術の発展段階に対応した開発の重要性について述べる.
著者
竹村 利夫 藤井 昭二
出版者
Japan Association for Quaternary Research
雑誌
第四紀研究 (ISSN:04182642)
巻号頁・発行日
vol.22, no.4, pp.297-312, 1984-02-29 (Released:2009-08-21)
参考文献数
38
被引用文献数
12 10

There are many active faults in central Japan. Several active faults distributed in the northern part of the Hida mountains are described in detail in this paper.The Atotsugawa, Mozumi and Ushikubi faults, 40-80km in length, are NE-ENE in trend and displaced to the right side. The amounts of horizontal displacement as revealed in the offsets of the streams crossing the fault lines are about 1-3km, and the amounts of vertical displacement are 100-300m with the northwest side upthrown.The Kazura fault, 30km long, is NNW in trend and displaced to the left side. The amount of horizontal displacement is 1km as recognized from the stream offset, and the amount of vertical displacement is 100-200m with the west side upthrown.The Atotsugawa fault has displaced the Pleistocene terraces and lake deposits (20, 000- 40, 000y.B.P.) as much as 50-60m vertically at the outcrops of the Magawa River area located up the Jyoganjigawa River. Also the Holocene terraces (about 500y.B.P.) have been displaced 1-4m vertically. The average vertical displacement rate of the Atotsugawa fault is 1-4m/1000y., and the average lateral displacement rate is 1-5.7m/1000y. as judged from the pitch θ of striation on the fault planes.Several outcrops are found along the Mozumi, Ushikubi and Kazura faults. Late Pleistocene and Holocene terraces have been cut and displaced by faults. The average rate of displacement was 0.4-1.5m/1000y. in vertical displacement. The lateral component of displacements are usually larger than or nearly the same as the vertical components.These faults can be ranked as A class or the upper half of B class in degree of activities.