著者

水垣 滋 中村 太士

出版者

日本地形学連合

雑誌

地形 = Transactions, Japanese Geomorphological Union (ISSN:03891755)

巻号頁・発行日

vol.20, no.2, pp.97-112, 1999-04-25

参考文献数

30

被引用文献数

10

著者

木下 祐介 八反地 剛 八木 勇治 江崎 隼輝 奥村 大輔

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.35, no.1, pp.25-39, 2014-01-25

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The 2011 East Japan Earthquake caused landslides across the Northern Kanto and Tohoku Regions. The purpose of the present study is to reveal the characteristics of shallow landslides induced by the earthquake and subsequent rainfall in granitic mountains located in northern Ibaraki Prefecture, Japan. Total 140 shallow landslides were identified through interpretation of aerial photographs and fieldwork. Among the 140 landslides, 65 were directly triggered by the main shock (March 11 to 18, 2011), and the rest 75 were triggered by rainfall events or other earthquakes from March 19 to December 15, 2011. The most of them are shallow landslides with a slip plane of granitic soil (grus). Bedrock or weathered bedrock is exposed on some landslide scars in the area underlain by biotite granite where soil is thinner. Among the 87 landslides, which occurred on natural hillslopes, 50 landslides slid eastward (NE to SE). The bias in landslide direction on natural hillslopes would correspond to the direction of crustal movement of the main shock.

著者

岡田 操

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.31, no.1, pp.17-32, 2010-01-25

参考文献数

19

被引用文献数

1

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String-flark (kermi-schlenke) complex pattern is a characteristic micro-topography in boreal mires. It consists of linear ridges aligned perpendicular to the slope, separated by water zones that are more sparsely vegetated. Various explanations for the formation process of this micro-topography have been proposed, however, the process by which oriented string-flark complex pattern originates is not clear. Nevertheless, as pattern formation occurs very slowly in nature, computer simulation offers useful help in understanding the formation process. In the present study, the formation processes have been defined by classifying the development stages of the string-flark complex pattern. While evaluating the existing theories on origin, a computer program has been coded to simulate using Carex Model, and verified the formation process. Carex Model is based on the growth processes of bog vegetation. Hence it can simulate changes in peat layers and thus predicts the formation of the diverse micro-topographies of mires. The result implies that string-flark complex pattern is generated by the accumulation of additional litter brought by snow-melting flow. Water level changes under the influence of prevailing hydraulic conditions and the patterns are formed with the selective growth of vegetation.

著者

中田 正夫 奥野 淳一

出版者

日本地形学連合

雑誌

地形 = Transactions, Japanese Geomorphological Union (ISSN:03891755)

巻号頁・発行日

vol.32, no.3, pp.327-331, 2011-07-25

参考文献数

4

被引用文献数

1

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During the growth of an ice sheet the continental crust beneath and near the ice sheet subsides, while in the decay period of glacier ice the crust is unloaded and rebounds. The process is called glacio-isostasy. The volume of sea water decreases during ice growth, while it increases during ice decay. The changing water load causes the vertical movement of the oceanic crust. The process is referred to as hydro-isostasy. These two processes combined are involved in glacio-hydro isostasy, i.e., the Earth's response to changes in ice and water loading during glacial cycle. The outline of a model for glacio-hydro isostasy is described and an application of the model to the northwestern Kyushu area is briefly introduced.

著者

小泉,武栄

出版者

日本地形学連合

雑誌

地形

巻号頁・発行日

vol.32, no.1, 2011-01-25

---

The Tamagawa Josui Canal was excavated in the early Edo period to conduct city water from the Tama River to Edo. In this canal there is a conspicuous asymmetry in slope morphology between both banks. That is, the left bank has steep cliff while the right bank has gradual slope with short cliff on upper part of the bank. To elucidate the cause and the forming process of the asymmetrical slope morphology, we investigated geomorphic surface process on each bank. During January 11th to December 24th in 2003, we set up traps on each bank and weighed monthly the volume of debris fallen down from upper part of the slopes. According to longitudinal measurement of debris volume, failure of soil surface occurs throughout the year on the slope of the both banks, though total amount of debris production on the left bank were twice as high as that on the right bank. Amount of debris in winter season was 9.7 times higher than in summer season. Especially from January to March, debris was intensively produced on the right bank. Debris production was evident to be induced by needle ice. Geomorphic surface processes on the north-facing right bank are as follows. In winter season, frost columns are formed on the surface of Kanto Loam (volcanic ash sediment) under low soil temperature and high soil moisture. A few days later, when needle ice melt, small grains are left on the surface of Kanto Loam. Grains are eventually carried down by the rainfall or winds to lower part of the slope. As a result, cliffs on upper part of the bank retreat and gentle slopes of the lower part expand. On the south-facing left bank, debris production is little throughout the year. On this bank, cliffs are so dried up in winter because of rich sunshine that needle ice don't arise even air temperature fell down under the freezing point. Instead, many cracks arise lengthways and blocks of soil fall down in occasion of heavy rain. In this way, the cliff retreats with its vertical shape. The Tamagawa Josui Canal is supposed to have maintained its original form when it had been brimmed with water, from the construction time till 1965 when water flow stopped by the disuse because of completion of filtration plant. After water flow was stopped and canal became to be dried up, asymmetry of the trench profile has been formed.

著者

豊田 新 成瀬 敏郎

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.23, no.5, pp.811-820, 2002-12-25

参考文献数

23

被引用文献数

15

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風成塵の主要鉱物である微細石英の電子スピン共鳴(ESR)分析によって最終氷期最盛期MIS 2と完新世MIS 1における日本列島および東アジア各地の堆積物を分析し,東アジアのジェット気流と北西季節風の挙動を復元した.MIS 2には韓国や瀬戸内海以北は酸素空格子信号強度が高く,シベリア高気圧から吹き出した北西季節風によって北部アジア大陸に広がった砂漠から風成塵が多量に運ばれた.瀬戸内海〜関東を結ぶ線から沖縄本島までは中国内陸砂漠から夏季亜熱帯ジェット気流によって風成塵が運ばれ,宮古島以南は中国南部あるいはチベット高原から冬季亜熱帯ジェット気流によって風成塵が運ばれた.台湾は第三紀が広く分布する台湾山脈から海岸にもたらされた酸素空格子信号強度の低い細粒物質が混入するために風成塵堆積物の信号強度が低い.当時はポーラーフロントの北限が瀬戸内海から関東を結ぶ地域にあった.MIS 1にはポーラーフロントが北海道まで北上したために,風成塵(黄砂)は中国内陸砂漠から韓国をはじめ,北海道にまで運ばれるようになった.

著者

宮縁 育夫 大丸 裕武 小松 陽一

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.25, no.1, pp.23-43, 2004-01-25

被引用文献数

3

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The 29 June 2001 rainstorm (total 238 mm; maximum hourly rainfall 98 mm) triggered more than 700 landslides and associated lahars at Aso Volcano, central Kyushu, SW Japan. Most of the landslides were concentrated in a 20-km^2 area that includes the northeastern slope of post-caldera central cones, the northern slope of Nekodake Volcano and the eastern caldera wall. We mapped landslides triggered by the storm using field observations and 1 : 20,000-scale aerial photography provided by the Kumamoto District Forest Office taken in December 2001. Most of the triggered landslides were shallow (about 1 m thick) soil slips in unconsolidated airfall tephra layers overlying lava flows and pyroclastic rocks. Average volume of the landslides was 550 m^3, but some had volumes exceeding 10,000 m^3. The rupture surfaces of most landslides were formed near the boundary between upper blackish and lower brownish tephra layers. These layers have differences in permeability, grain size and soil hardness. Most landslides mobilized completely into lahars, traveling a few kilometers along stream channels. Although some lahars eroded channel side slopes and transported boulders (2-3 m in diameter), most contained up to about 80 percent silt-to-clay-size particles, similar in composition to the original landslide debris. Sediment discharge volumes by the tephra-slip-induced lahars were estimated at an order of 10^3-10^4 m^3/km^2 using sediment volumes trapped by check dams. These volumes are similar or one-order of magnitude smaller than the volumes of the 1953 and 1990 landslide disasters in the same region. The characteristics of landslides and lahars and their estimated volumes provide important information about landslide and lahar hazards at Aso Volcano.

著者

藁谷,哲也

出版者

日本地形学連合

雑誌

地形

巻号頁・発行日

vol.26, no.3, 2005-07-25

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Weathering environment at two study sites of Angkor Wat were analysed together with mineralogical and physico-chemical behaviour of building stones of sandstone and laterite. In order to store the set of data of air temperature and relative humidity at intervals of 30 minutes, two data loggers were installed at Elephant gate (Site 1) and West causeway (Site 2), between 5 September 2000 and 10 September 2001. The results show that Site 1 had more severe temperature and humidity changes (-5℃/30min, 24%/30min in maximum) than Site 2 (-4℃/30min, 19%/30min). In addition, Site 1 had a high frequency of wetting and drying cycles (73 cycles) compared to Site 2 (6 cycles). These measurements argue that wet-dry alternation and salt efflorescence are major in exfoliation on sandstone surfaces at Elephant gate. The laterite composed of goethite, hematite, quartz and kaolinite has no swelling clay minerals. However, the laterite has small tensile strength (1.2 MPa) than the sandstone (3.5 MPa), as well as low durability for wet-dry repetition. It is recognized that slaking of the laterite due to fluctuation in water level at the moat has caused subsidence of West causeway.

著者

津村 宏臣

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.25, no.3, 2004-07-25

著者

鈴木 元 笠木 勇祈 鈴木 隆介

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.27, no.4, pp.515-516, 2006-10-25

著者

小泉 武栄 伊東 敦子

出版者

日本地形学連合

雑誌

地形 = Transactions, Japanese Geomorphological Union (ISSN:03891755)

巻号頁・発行日

vol.32, no.1, pp.1-14, 2011-01-25

参考文献数

14

---

The Tamagawa Josui Canal was excavated in the early Edo period to conduct city water from the Tama River to Edo. In this canal there is a conspicuous asymmetry in slope morphology between both banks. That is, the left bank has steep cliff while the right bank has gradual slope with short cliff on upper part of the bank. To elucidate the cause and the forming process of the asymmetrical slope morphology, we investigated geomorphic surface process on each bank. During January 11th to December 24th in 2003, we set up traps on each bank and weighed monthly the volume of debris fallen down from upper part of the slopes. According to longitudinal measurement of debris volume, failure of soil surface occurs throughout the year on the slope of the both banks, though total amount of debris production on the left bank were twice as high as that on the right bank. Amount of debris in winter season was 9.7 times higher than in summer season. Especially from January to March, debris was intensively produced on the right bank. Debris production was evident to be induced by needle ice. Geomorphic surface processes on the north-facing right bank are as follows. In winter season, frost columns are formed on the surface of Kanto Loam (volcanic ash sediment) under low soil temperature and high soil moisture. A few days later, when needle ice melt, small grains are left on the surface of Kanto Loam. Grains are eventually carried down by the rainfall or winds to lower part of the slope. As a result, cliffs on upper part of the bank retreat and gentle slopes of the lower part expand. On the south-facing left bank, debris production is little throughout the year. On this bank, cliffs are so dried up in winter because of rich sunshine that needle ice don't arise even air temperature fell down under the freezing point. Instead, many cracks arise lengthways and blocks of soil fall down in occasion of heavy rain. In this way, the cliff retreats with its vertical shape. The Tamagawa Josui Canal is supposed to have maintained its original form when it had been brimmed with water, from the construction time till 1965 when water flow stopped by the disuse because of completion of filtration plant. After water flow was stopped and canal became to be dried up, asymmetry of the trench profile has been formed.

著者

青木 久 松倉 公憲

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.25, no.3, pp.267-276, 2004-07-25

被引用文献数

8

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We introduce the equotip hardness tester and present the relations between the Equotip rebound value (L-value) and the unconfined compressive strength (UCS) for intact rock samples. Based on existing data and the results of our laboratory tests, an equation is derived connecting UCS (MPa) and L-value obtained from single impacts, L_s, and porosity, n (%), using multiple linear regression analysis: it is found that UCS = 0.079 e^<-0.039n> L_s^<1.15>

著者

恩田 裕一 古賀 聡子 福山 泰治郎 平松 晋也 長嶺 真理子 水野 秀明 原槇 利幸

出版者

日本地形学連合

雑誌

地形

巻号頁・発行日

vol.26, no.3, 2005

著者

岡田 操

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.29, no.3, pp.281-300, 2008-07-25

被引用文献数

2

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In bog mires, peat formation depends largely on plant growth, the amount of which in turn is influenced by rates of primary production, soil pH, sunlight, and ground, air and water temperatures. Plant growth is also affected by soil saturation and thus groundwater, which in turn are influenced by meteorological factors such as precipitation and evapotranspiration as well as hydrological factors such as inflow, outflow and storage. The flow of groundwater is influenced by peat composition, where a lack of water results in plant death, followed by partial decomposition of plant matter. This accumulates contributing to the upper layers of peat. As time progresses, the plant matter undergoes varying degrees of decomposition and consolidation producing peat of variable density, porosity, and permeability. The model proposed in this paper focuses on groundwater table, the most significant factor in peat formation. The characteristic of this model is the determination of the relationship between plant growth and groundwater table under variable conditions. In a given topographical configuration, if boundary conditions such as the inflow and outflow of rainfall and surface soil are manipulated, unsteady flow calculations reveal changes in water level. If this is iterated for an entire season, vegetation grow and peat will accumulate depending on the mean seasonal water level. This relationship is predicted using the growth function of vegetation, which is determined from growth simulations incorporating actual data from the primary production of specific plants. Iterated over the course of several years the thickness of peat layers gradually changes, giving rise to a conspicuous topography. This model demonstrates that causes of topographical formation, which to date could only be determined qualitatively can now be done quantitatively. Based on the growth processes of bog vegetation, this paper proposes a "Carex Model", which simulates changes in peat layers and thus predicts the formation of the diverse micro-topographies of bog mires.

著者

倉茂 好匡 池尻 公祐 鈴木 幸恵 平川 一臣

出版者

日本地形学連合

雑誌

地形 = Transactions, Japanese Geomorphological Union (ISSN:03891755)

巻号頁・発行日

vol.26, no.2, pp.131-149, 2005-04-25

参考文献数

19

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当縁川流域での農業開墾は1894年に開始され, その後この流域内の農地面積は1930年ごろより激増した.一方, 当縁川下流部にある湿原内では1986年から1920年の間に蛇行流路の切断が生じ, このため開墾開始後に運搬されてきた土砂が新流路側方に堆積して自然堤防を形成した.この自然堤防堆積物の層序構造観察とその粒径組成および137Cs濃度の分析を行った結果, 砂質物質の堆積が1930年代終わりごろより開始されたのに対し, それ以前の堆積物はシルト質のものであることが判明した.この砂質堆積物に対して粒径分布トレーサー法を用いてその給源を推定したところ, 砂質堆積物は支流である忠類幌内川流域から主に流出してきていることがわかった.また, 本流のうち1980年代に直線化された区間も砂質堆積物の重要な給源となっていた.それに対し, 本流上流部からの砂質堆積物の供給量は少なかった.忠類幌内川流域の農地は, 第三紀層よりなる豊頃丘陵を刻む谷の谷底部付近にのみ存在している.それに対し, 本流上流部の農地は扇状地上に存在する.これらのことから, 特に豊頃丘陵の谷底部で行われた集中的な農地開墾が大きな砂質堆積物流出を招いたと判断した.

著者

横山 勝三 Shozo YOKOYAMA

出版者

日本地形学連合

雑誌

地形 = Transactions, Japanese Geomorphological Union (ISSN:03891755)

巻号頁・発行日

vol.34, no.4, pp.303-311, 2013-10-25

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阿蘇カルデラの外輪山には多数の安山岩質岩塔(トア)が見られる.その多くは,きわめて強く帯磁しており,その強い磁性はクリノメーターを使って容易に捉えられる.この強く帯磁した岩石すなわち磁石石は,落雷の影響で生じたと思われる.これらの磁石石(トア)の上面には風化穴(weathering pit,ナマ)がみられるものがある.一方,落雷の近年の報道には,花崗岩やコンクリートなどの建造物に損傷を与えた事例がある.また,いくつかの空港の滑走路上に落雷で小孔が生じた事例も報告されている.このような落雷の破壊力から判断すると,落雷で岩石表面に孔が生じる可能性はきわめて高い.これらのことから,磁石石上の風化穴は,落雷による最初の小孔(initial depression)の形成から始まったと考えられる.Numerous tors of andesite are found on the somma of Aso caldera, Kyushu, Japan. Many of them are very strongly magnetized as can be detected easily by a geologic compass. Such strongly magnetized rocks, namely lodestones, are presumed to have been formed by the effect of lightning strike. Weathering pits are found on some of the top surfaces of the lodestone tors. According to the recent reports, there are examples of lightning strikes which damaged constructions of granite and concrete. Also, pits on runways formed by lightning strikes have been reported from some airports. Judging from the destructive power of lightning strikes, it is highly probable that pits are formed on rock surfaces by lightning strikes. Thus, it is interpreted, from these, that the weathering pits on the lodestones started from initial depressions formed by lightning strikes.

著者

中村 太士 中野 大助 河口 洋一 稲原 知美

出版者

日本地形学連合

雑誌

地形 = Transactions, Japanese Geomorphological Union (ISSN:03891755)

巻号頁・発行日

vol.27, no.1, pp.41-64, 2006-01-25

参考文献数

111

被引用文献数

4

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River ecosystem is spatiotemporally dynamic under frequent and intensive geomorphic disturbances, characterized by its fluctuating habitat availability. The species inhabiting there adapt themselves to the shifting habitat by developing various life-history strategies. In regulated rivers, however, suppressed disturbance and habitat dynamics threaten the disturbance-dependent communities. The recognition of important geomorphic perspectives is still in its infancy in conservation of river ecosystems in Japan. Riparian tree species have developed life-history strategies to increase the likelihood of arriving regeneration sites, where disturbance regimes are closely linked to the spatial and temporal availability of regeneration sites. River damming and channel modification severely diminish the critical function of geomorphic disturbance sustaining habitat diversity and abundance. Channel migration ceases in flow-regulated rivers, which may temporarily promote expansion of pioneer forest in the active channels. However, new geomorphic surfaces suitable for establishment of seedlings are no longer created because of altered peak flows and sediment supply, thereby threatening the recruitment opportunity and ultimate survival of their populations. Suppression of geomorphic disturbance also leads to the degradation of in-stream fauna. Channel straightening particularly simplifies geomorphic features of a river reach and diminishes longitudinal and lateral habitat diversity in its active channel. Flood control reduces inundation habitat and disrupts hydrologic connectivity between floodplain habitats (e.g., backwater and oxbow lakes), impacting fish and benthic invertebrates that require those habitats in their various life stages. A channel re-meandering experiment in the Shibetsu River, Hokkaido, demonstrates that the recovery of geomorphic dynamics can play significant roles in restoration of river ecosystems. Meandering reaches develop shallow edge habitat with low hydraulic stress along the inside of a convex, providing stable substrate for macroinvertebrate communities. Fallen trees provided by lateral erosion also promote macroinvertebrate colonization and become in-stream covers for fish communities. Geoecology in Japan as well as Europe and U.S. has long focused on vegetation pattern in alpine regions and has unexplored terrestrial and aquatic ecosystems in the vicinity of human activities. Knowledge in habitat dynamics and geomorphic processes is vital to ecosystem conservation and restoration. We believe that participation of geomorphologists is essential in future development of conservation and restoration strategies.

著者

宮崎 裕子 千木良 雅弘 黒川 潮

出版者

日本地形学連合

雑誌

地形 = Transactions, Japanese Geomorphological Union (ISSN:03891755)

巻号頁・発行日

vol.26, no.3, pp.205-224, 2005-07-25

参考文献数

36

被引用文献数

1

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The Niijima and Kozushima earthquake struck Kozushima Island to the south of Tokyo on 1 July 2000, with an intensity of 6-low on the Japanese Meterological Agency scale. The earthquake was followed by heavy rain (cumulative storm precipitation 291mm in 24 hour and maximum hourly precipitation 52mm) on July 7th to 8th and another earthquake occurred on July 9th. These cumulative events triggered many landslides, which we identified on air photographs taken before, during, and after the events, and then mapped on GIS-based topographic and geologic maps to assess the cumulative effects of consecutive earthquake and rainfall on slope failures on a rhyolitic volcano. The successive July 1st earthquake, rainfall, and smaller July 9th earthquake triggered 618, 123, and 102 slope failures, respectively, on rhyolitic lava and pyroclastics that dominate the island. Most of the failures occurred on slopes steeper than 30 degrees near the "erosion front". On jointed rhyolite lava slopes, many earthquake-initiated slope failures occurred because of the high inertial energy within the lava mass during the earthquake. Conversely, few landslides were triggered by rainfall because of the high permeability of the lava. Areas of coarse pyroclastics and crumble breccia suffered from many landslides during the first earthquake but not during the subsequent rainstorm, probably due to the low cohesion and large permeability of these materials. Alternatively, silt or clay-rich pyroclastics experienced more landslides during rainfall compared to the earthquake because of the greater cohesion and lower permeability of these materials. However, rainfall on July 7th to 8th alone appears not to be of sufficient intensity to trigger widespread landslide; previous rainfall events that initiated widespread slope failures on the Kozushima Island had maximum 1-hour intensities >100mm. The earthquake on July 1st could have loosened the surface material, which failed during the subsequent moderate rainfall.

著者

中田,正夫

出版者

日本地形学連合

雑誌

地形

巻号頁・発行日

vol.32, no.3, 2011-07-25

---

During the growth of an ice sheet the continental crust beneath and near the ice sheet subsides, while in the decay period of glacier ice the crust is unloaded and rebounds. The process is called glacio-isostasy. The volume of sea water decreases during ice growth, while it increases during ice decay. The changing water load causes the vertical movement of the oceanic crust. The process is referred to as hydro-isostasy. These two processes combined are involved in glacio-hydro isostasy, i.e., the Earth's response to changes in ice and water loading during glacial cycle. The outline of a model for glacio-hydro isostasy is described and an application of the model to the northwestern Kyushu area is briefly introduced.

著者

西山 賢一 横田 修一郎 横山 勝三

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.25, no.3, 2004-07-25