Deep-seated rockslide-avalanches preceded by mass rock creep of sedimentary rocks in the Akaishi Mountains, central Japan

1994 ◽  
Vol 38 (3-4) ◽  
pp. 221-230 ◽  
Author(s):  
Masahiro Chigira ◽  
Kenzo Kiho
Keyword(s):  
Sedimentary Rocks ◽  
Central Japan ◽  
Rock Creep ◽  
Mass Rock

scholarly journals The 1998 Tatopani Landslide in the Kali Gandaki Valley of Western Nepal: cause and relation to mass rock creep

2000 ◽  
Vol 22 ◽  
Author(s):  
Hellmut R. Volk
Keyword(s):  
Slope Instability ◽  
Low Grade ◽  
Left Bank ◽  
Main Central Thrust ◽  
Slope Movements ◽  
Wedge Failure ◽  
Rock Avalanches ◽  
Rock Creep ◽  
Mass Rock ◽  
The Village

The village of Tatopani lies on a small gravel terrace in the middle reach of the Kali Gandaki River, along a narrow course of about 2 km in length. One kilometre south of the village, a major rockfall occurred recently in the region of the Lesser Himalaya, which is built up of low-grade metamorphic rocks of the Kuncha Group, consisting of a thick sequence of foliated phyllites and bedded quartzites as well as interlayering of both lithologies. The monoclinal structure of these metasedimentary rocks is clearly related to the general trend of the Nepal Himalaya near the Main Central Thrust (MCT): strike NW-SE 140- 150°, dip 25-45° NE. Besides a clear foliation in the phyllites (s1) parallel to the quartzite bedding (s0), four other discontinuities are also developed as steep joints (j1-j4). Two joint sets j1 and j2, both crossing each other and both acting in conjunction with the foliation (s1) as a shear plane, were responsible for the wedge failure of the Tatopani Landslide, which led to a rockfall and avalanche of about 400,000 cubic metres and dammed the river for about 72 hours. It is noteworthy that several other - strikingly similar but older - weathered wedge failure surfaces are exposed at various spots all over the same ridge, which is the spur-ridge dividing the Kali Gandaki River from the Gar Khela tributary. This visible slope instability evidenced by relatively small wedge failures is causally connected with a much larger mechanism, namely mass rock creep or "sagging"- a purely gravitational slope deformation. The repeatedly occurring wedge failures producing landslides (rockfalls and rock avalanches) are caused by extreme shear stress and deep-reaching joints and fissures during mass rock creep. Only the final trigger for landslides or rockfalls is provided by extreme and lengthy monsoon rainstorms, which reinforce the cleft-water pressure inside rock discontinuities and openings, especially along the impermeable interface of quartzites and phyllites (s0 =s1) at the base of the wedge failure. The right (western) bank above the village is morpho-dynamically active also through mass rock creep and “pushes” laterally against the river course. However, the kinematics of the rock slope is rather different because the foliation geometry is more important. The foliation dips obliquely towards the riverside and consequently has facilitated extremely slow large­ scale dip slope movements along quartzite-phyllite interfaces (s0) without any catastrophic danger. However, the creeping slope movements of thick quartzite: members caused a set of conjugate extension faults producing toppling at the distal slope margins. Rock avalanches from the spur-ridge on the eastern (left) bank of the Kali Gandaki River S of Tatopani will always remain a threat, especially when excessive seasonal rains increase the cleftwater pressure inside the invisibly slow creeping system of the steep bank in an extraordinary manner.

scholarly journals Geology and age of the Neogene sedimentary rocks in the Ituskaichi Basin, central Japan

1990 ◽  
Vol 96 (9) ◽  
pp. 759-770_1 ◽  
Author(s):  
Toshiaki IRIZUKI ◽  
Masaki TAKAHASHI ◽  
Yuichiro TANAKA ◽  
Motoyoshi ODA
Keyword(s):  
Sedimentary Rocks ◽  
Central Japan

The Redox Environment of Deep Groundwaters Associated with the Tono Uranium Deposit, Japan

2002 ◽  
Vol 713 ◽  
Author(s):  
Randy Arthur ◽  
Teruki Iwatsuki ◽  
Katsuhiro Hama ◽  
Kenji Amano ◽  
Richard Metcalfe ◽  
...  
Keyword(s):  
Uranium Deposit ◽  
Sedimentary Rocks ◽  
Redox Potentials ◽  
Central Japan ◽  
Flow Models ◽  
The Past ◽  
Oxidation Reduction ◽  
Reversible Redox ◽  
Approximate Location

ABSTRACTAn unconformity underlying the Tono uranium deposit in central Japan represents the approximate location of a redox front separating relatively oxidizing groundwaters (Eh ≈0 mV) in the weathered, fractured Toki granite (TG) from strongly reducing pore fluids (Eh ≈-360 mV) in sedimentary rocks of the overlying Lower Toki Lignite-bearing Formation (TL). Uranium has been effectively immobilized in the TL during the past 10 million years. Stable and reversible redox potentials measured in-situ in boreholes penetrating the sedimentary rocks and granite appear to be controlled by the Fe(III)-oxyhydroxide – Fe2+ redox couple. A simplified analytical model of front migration suggests that chemical buffering by pyrite alone would limit the propagation velocity of the front into the TL to less than 8x10−6 m yr−1. The model is constrained by Darcy fluxes derived from groundwater flow models and relative 14C groundwater ages, average modal abundances of pyrite in the TL, and the analytical detection limit for dissolved oxygen in TG groundwaters (2 ppm). Model results also suggest that the redox buffering capacity of the TL would be exhausted within 10 million years if an upper bound O2(aq) concentration in TG groundwaters fixed by equilibrium with atmospheric O2(g) (8.5 ppm) is assumed. Immobilization of uranium in the TL is thus attributable to oxidation-reduction reactions that minimize O2(aq) concentrations primarily in the TG, and secondarily in the TL.

Thermal monitoring to infer possible interactions between shallow hydrothermal system and slope-scale gravitational deformation of Mt. Epomeo (Ischia Island, Italy)

2021 ◽  
pp. SP519-2020-131
Author(s):  
M. Della Seta ◽  
C. Esposito ◽  
M. Fiorucci ◽  
G. M. Marmoni ◽  
S. Martino ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Inverse Correlation ◽  
Local Stress ◽  
Slope Instability ◽  
Thermal Monitoring ◽  
Monthly Basis ◽  
Content Type ◽  
Rock Creep ◽  
Supplementary Material ◽  
Mass Rock

AbstractGeothermal and volcanic systems are prone to gravity-induced slope instability at different scales. Endogenous magmatic, hydrothermal, and seismic forcings can significantly modify mechanical properties and perturb the local stress field and gravitational equilibrium inducing shallow or slope-scale instabilities. The island of Ischia, which is part of the Phlegrean Volcanic District (Italy), is a remarkable example of this kind of complex interacting system. This study focuses on monitoring the hydrothermal system located beneath the ongoing slope-scale deformation, which involves Mt. Nuovo (the western part of Mt. Epomeo) and is a complementary effect of the resurgence of an ancient caldera. Debris and rock avalanches have affected the slopes of this volcanic island, in response to the renewal of volcanic activity and caldera resurgence. Large parts of the corresponding mass-wasting deposits overlay the most active areas of the Ischia hydrothermal system, where ongoing slope-scale gravity-driven deformation due to a mass rock creep (MRC) process is still evolving. To investigate possible relations between the perturbing shallow hydrothermal system and the MRC process, thermal monitoring of selected groups of fumarolic emissions located in several portions of the deforming sector has been carried out since 2008 on a monthly basis by means of direct (thermal probes) and remote sensing (IR-thermography) techniques. Thermal monitoring of specific fumaroles shows a peculiar seasonal trend characterised by a delayed inverse correlation with rainy periods and a short-term pulsating response to dry stages. The fumaroles also appear spatially correlated to the presence of MRC-related structures involving volcanic slopes. According to the measured thermal data, a conceptual model of the thermal interactions within the Mt. Nuovo slope is provided, framing the potential role of thermal actions in accelerating the deformation process. In this view, possible hazard scenarios, due to magmatic or hydrothermal renovation are depicted, delineating the interconnected multi-hazard worst scenario consisting of an accelerating evolution of the MRC process towards paroxysmal collapse.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5497819

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