Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.3313/jls.54.259

researchmap

Language：Japanese   Publisher：The Japan Landslide Society  

DOI： 10.3313/jls.53.109

CiNii Article

CiNii Books

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Freezing and thawing processes play an important role for the gravitational transport of surface materials on steep mountain slopes in Japan. The effects of deforestation on frost heave activity were observed through the 2012/2013 winter season in Ikawa University Forest, a southern mountainous area in central Japan (1180-1310 m above sea level). During periods without snow cover, needle ice development prevailed at a clear-cut site, and the downslope sediment movement of upper soil was 10 to 15 cm through the winter season. At a non-cut site, rise and fall in the ground surface level prevailed on a weekly scale, with no evident downslope movements at the surface; ice lens formation in the soil layer is assumed. Abrupt changes in the radiation budget, such as the strengthening of nighttime radiative cooling and increases in daytime direct insolation, induced frequent development/deformation of needle ice at the clear-cut site. In snow-free periods, the day-to-day variability in needle ice growth length and in nighttime averaged net radiation showed significant correlations; cloudy weather with warmer and moist air intrusion associated with synoptic disturbances prevented the occurrence of needle ice. Namely, day-to-day weather changes directly affected the mass movement of the upper soil after deforestation. Shallow snow cover occurred discontinuously through the winter and is likely an important factor in keeping the soil moisture sufficiently high in the upper soil layer for initiating needle ice during snow-free periods. We also discuss contributions of coastal extratropical cyclone activities providing both snow cover and cloudy weather in the southern mountain areas of central Japan to the intra-seasonal variability in frost heave and its indirect effect on soil creep and landslides on the deforested steep slopes. Copyright (c) 2015 John Wiley & Sons, Ltd.

DOI： 10.1002/esp.3776

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Characteristic landscapes (e.g., cuesta, cliff and overhang of caprock, or stepped terrain) formed by differential erosion can be found in areas composed of variable geology exhibiting different resistances to weathering. Parallel retreat of slopes, defined as recession of slopes without changes in their topography, is sometimes observed on slopes composed of multiple strata. However, the conditions needed for such parallel retreat have not yet been sufficiently clarified. In this study, we elucidated the conditions for parallel retreat of rock slopes composed of alternating layers using a geometric method. In addition, to evaluate whether various rock slopes fulfilled the conditions for parallel retreat, we analyzed topographic data obtained from periodic measurement of rock slopes in the Aka-kuzure landslide, central Japan. Our geometric analysis of the two-dimensional slopes indicates that dip angle, slope gradient, and erosion rate are the factors that determine parallel retreat conditions. However, dip angle does not significantly affect parallel retreat conditions in the case of steep back slopes (slope gradient > 40 degrees). In contrast, dip angle is an important factor when we consider the parallel retreat conditions in dip slopes and gentler back slopes (slope gradient < 40 degrees). Geology in the Aka-kuzure landslide is complex because of faulting, folding, and toppling, but spatial distribution of the erosion rate measured by airborne LiDAR scanning and terrestrial laser scanning (TLS) roughly fulfills parallel retreat conditions. The Aka-kuzure landslide is characterized by repetition of steep sandstone cliffs and gentle shale slopes that form a stepped topography. The inherent resistance of sandstone to weathering is greater than that of shale. However, the vertical erosion rate within the sandstone was higher than that within the shale, due to direct relationship between slope gradient and vertical erosion rate in the Aka-kuzure landslide. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.geomorph.2015.02.030

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Tokyo Geographical Society  

Sackung features (scarps) have developed extensively in the Japanese Alps as a result of gravitational deformation. Electrical resistivity tomography was applied to evaluate the internal structure below eight scarps located above 2600 m a.s.l. The range of resistivity values differed significantly between the scarps and is mainly controlled by the moisture content of the ground. High- and low-resistivity areas were distinctly separated below some scarps. Areas of relatively low resistivity are considered as slightly fractured bedrock. In contrast, areas of high resistivity are likely to indicate highly fractured bedrock and/or talus without matrix. Such boundaries between high- and low-resistivity areas seem to correspond to fracture planes estimated from topography.

DOI： 10.5026/jgeography.122.755

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/10023208833?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Tokyo Geographical Society  

This review paper synthesizes geomorphic dynamics, sediment transport and resulting natural hazards in mountains of the southern Japanese Alps and their drainage basins, where climatic and geological situations produce highly active landform dynamics. In alpine areas above the timber line, shallow diurnal freeze-thaw action operating in the thin topsoil produces small-scale periglacial forms, and gravitational spreading leads to numerous sackung features where snow-melt and heavy rain in places promote rockslides. In subalpine and montane areas, deep-seated landslides originate from fractured sedimentary rocks, deep V-shaped valleys, and heavy rain, while shallow landslides continue with historical forest clearance. Continuous slope failures prevent vegetation recovery and maintain debris input to valleys. Steep valleys contribute to high-density debris flows. Frequent or repetitive occurrences of these mass movements promote continuous denudation of slopes, rockfall accidents along hiking trails, and sedimentation at artificial dams. They occasionally cause significant hazards to villages further downstream. Predicting and mitigating slope hazards require distinguishing among annual, low-magnitude processes, episodic high-magnitude processes and geomorphic changes associated with long-term climate change.

DOI： 10.5026/jgeography.122.591

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/10023208710?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

The Aresawa rockslide in the Japanese Alps encountered a deep, partial collapse during an early snow-melting period in May 2004, followed by further progressive movement of the headscarp area. This paper reconstructs the pre-failure topography of the Aresawa rockslide based on the analysis of aerial photographs taken in multiple periods, and analyzes the factors controlling the threshold for the 2004 collapse. At least seven months before the collapse, new tension cracks emerged about 25 m behind the headscarp as a result of downslope movement of an unstable rock slab 5-10 x 10(5) m(3) in volume, accompanied by the development of a slip plane below a pre-existing shallow trough (sackung feature). The collapse finally occurred when progressive weakening of the rock mass was combined with water infiltration into the ground during rapid snow melting.

DOI： 10.1007/s10346-012-0353-5

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

The Aresawa rockslide in the Japanese Alps experienced a partial collapse (510 x 105?m3) in 2004, followed by an accelerated downward movement of the head area rather than stabilization. This paper discusses the kinematics of a retrogressive rockslide area and factors promoting slope instability subsequent to the 2004 collapse, on the basis of geodetic surveys and meteorological observations from 2006 to 2010. The unstable area covers at least 2.3 x 104?m2 and consists of five active blocks. The main blocks are separated from the stable rock slope by pre-existing sackung features that follow the strike of the bedding plane. Shear zones below these sackung features have developed into slip planes potentially causing the next collapse. In particular, the propagation of a slip plane causing movement at 70?cm?yr-1 in the head area is promoted by bidirectional movement. It consists of slow dip-slip movement in snow-accumulating periods and rapid side-slip movement in snow-melting and snow-free periods, both of which occur on the same slip plane. This bidirectional movement appears to result from the combination of a loss of lateral support by the 2004 event and the immature state of the slip plane. The primary trigger of the acceleration in the unstable area is the stress release by the 2004 collapse. In addition, the presence of a potential slip plane below the sackung features also promotes slope instability, suggesting that sackung features behind a rockslide area may predefine the new head scarp of a forthcoming collapse. Copyright (C) 2012 John Wiley & Sons, Ltd.

DOI： 10.1002/esp.3298

Web of Science

researchmap

DOI： 10.4116/jaqua.50.309

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The Aresawa rockslide in the Japanese Alps, which partially collapsed in May 2004, produced a number of new tension cracks in the head area. This paper discusses the dynamics of the rock slope and controls on the surface velocity, based on the results of on-site monitoring of the surface movement and meteorological parameters (air and ground surface temperatures, precipitation and snow depth). The rock mass deformation progressed at ca. 60 cm yr(-1) mainly along a slip plane dipping downslope at ca. 50 degrees. The surface velocity of the slipping rock mass showed a significant seasonal variation in response to the water infiltration. The velocity was small (<= 1 mm day(-1)) in winter. Subzero air temperatures and a heat-insulating snow cover, and resulting growth of seasonal frost, prevent water infiltration into the bedrock and contribute to the rock slope stability. Most of the movement in this period is attributed to gravitational deformation originating from the overburden pressure. In contrast, the surface velocity increased (up to 10 mm day(-1)) during snow-melting and snow-free periods. Snowmelt and rainfalls promote water infiltration into the bedrock, destabilizing the rock slope and accelerating the rock slip. Such a rapid movement is attributed to water-induced sliding superimposed on gravitational deformation. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.enggeo.2010.06.014

Web of Science

researchmap

Language：Japanese   Publisher：Tokyo Geographical Society  

Linear depressions and associated uphill-facing scarps, which result from the gravitational deformation of rock slopes, have widely developed along the main ridge in the Mt. Eboshi area, northern Japanese Alps. The role of landslides in the development of linear depressions in granitic rocks is evaluated from the distribution of linear depressions, characteristics of landslides (form, magnitude and frequency) and characteristics of bedrock (geology, discontinuity, degree of weathering and rock mass strength). The morphology of landslides and changes in the areas of landslides from 1958 to 2004 are compared to the development of linear depressions. Most linear depressions lie parallel to the main ridge and the strike of major rock joints, although their distribution differs between the northern and southern areas. In the northern study area, linear depressions are concentrated on the gentle upper slopes and landslides have intensively occurred on the lower slopes. In contrast, the southern area shows sporadic occurrences of linear depressions on the middle to upper slopes and has experienced only minor landslides. The intensive occurrences of landslides and linear depressions in the northern area are considered to result basically from debuttress and stress-release caused by the landslide activity. In addition, the lower rock mass strength in the northern study area also promotes the development of linear depressions.

DOI： 10.5026/jgeography.118.233

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00330973494?from=CiNii

Language：Japanese   Publishing type：Research paper (scientific journal)  

Weathering characteristics of two kinds of granites and their influences on landforms are compared along the main ridge of the Mt. Noguchi-goro area, the northern Japanese Alps. The two lithologies (granites A and B) contrast in the Schmidt rock hammer rebound, P-wave velocity, weathering index and physical rock properties. The granite A has lower rock strength and produces finer rock debris composed mainly of pebbles and finer materials than the granite B, reflecting the difference in the mineral composition. The granite A is subject to granular disintegration resulting from the high content of plagioclase that is sensitive to weathering. In contrast, the granite B produces a wide range of rock debris sizes from pebbles to boulders, reflecting the high content of K-feldspar that is less susceptible to granular disintegration and the predominance of macrogelivation along joints. The weathering characteristics of the two lithologies affect the types and morphology of the alpine landforms in the area, including patterned grounds, tors and mass movement features. For instance, the fine and homogeneous sizes of debris lead to the predominance of sorted stripes on slopes in the granite A area, while the wide range of debris sizes is responsible for turf-banked terraces in the granite B area. The contrasting weathering features indicate that chemical weathering plays an important role in the grain size distribution of surface materials as well as frost shattering.

CiNii Article

CiNii Books

researchmap

Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10807706

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

This paper describes a rockfall event in the Daisekkei Valley of Mount Shirouma-dake (2,932 m), the northern Japanese Alps. The rockfall occurred on a steep cliff comprising well-jointed felsites and produced debris of >= 8,000 m(3). Most debris was deposited on an elongated snowpatch located immediately beneath the cliff, and it caused casualties among people who were trekking along a trail on the snowpatch. Additionally, a large rock block slipped 1 km on the snowpatch. The rockfall could have been due to the differential retreat of the rockwall, which contains areas of high- and low-density joints. Seasonal and diurnal freeze-thaw activities and snow avalanches and wash appear to be important factors responsible for the retreat. Although some rock blocks that can collapse further remain on the rockwall, the position of the mountain trail in the Daisekkei Valley is fixed. Fundamental reform of tourism systems for climbers, including education on natural hazards, is required.

DOI： 10.1007/s10346-006-0067-7

Web of Science

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

researchmap

researchmap

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Other Link： http://id.nii.ac.jp/1141/00111073/

Language：Japanese  

CiNii Article

CiNii Books

researchmap

Other Link： http://id.nii.ac.jp/1141/00110870/

Language：Japanese   Publisher：日本地形学連合  

CiNii Article

CiNii Books

researchmap

Other Link： http://id.nii.ac.jp/1141/00110807/

Language：Japanese  

CiNii Article

CiNii Books

researchmap