scholarly journals Geotechnical Distinction of Landslides Induced by Near-Field Earthquakes in Niigata, Japan

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Hirofumi Toyota ◽  
Susumu Takada
Keyword(s):  
Public Service ◽  
Debris Flows ◽  
Near Field ◽  
River Channels ◽  
Dam Breaks ◽  
Geological Features ◽  
Natural Dam ◽  
The Stability ◽  
Heavy Damage ◽  
Emergency Measures

Landslides triggered by near-field earthquakes with epicentres directly beneath towns have attracted intense attention since the 2004 Mid-Niigata (Niigata-ken Chuetsu) Earthquake. Hilly and mountainous areas sustained heavy damage. Social problems developed when many towns became isolated because landslides cut off traffic and public service lifelines. Soil from landslides closed river channels and formed natural dams. The natural dams submerged some towns. Emergency measures were undertaken promptly to prevent debris flows caused by natural dam breaks. Subsequently, the 2007 Mid-Niigata Offshore (Niigata-ken Chuetsu-oki) Earthquake and the 2011 Northern Nagano Earthquake struck the Niigata region. Landslides triggered by those earthquakes differed in terms of their number, scale, and location. Therefore, characteristics of the landslide sites of the respective earthquakes were examined to ascertain their topographical and geological features. Furthermore, differences in groundwater level and damage related to compound disasters were explained for discussion of the stability progress of damaged slopes.

scholarly journals Coherent suppression of backscattering in optical microresonators

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Andreas Ø. Svela ◽  
Jonathan M. Silver ◽  
Leonardo Del Bino ◽  
Shuangyou Zhang ◽  
Michael T. M. Woodley ◽  
...  
Keyword(s):  
Quality Factor ◽  
Bulk Material ◽  
Near Field ◽  
High Quality Factor ◽  
Dual Frequency ◽  
High Quality ◽  
Frequency Combs ◽  
Optical Microresonators ◽  
Whispering Gallery ◽  
The Stability

AbstractAs light propagates along a waveguide, a fraction of the field can be reflected by Rayleigh scatterers. In high-quality-factor whispering-gallery-mode microresonators, this intrinsic backscattering is primarily caused by either surface or bulk material imperfections. For several types of microresonator-based experiments and applications, minimal backscattering in the cavity is of critical importance, and thus, the ability to suppress backscattering is essential. We demonstrate that the introduction of an additional scatterer into the near field of a high-quality-factor microresonator can coherently suppress the amount of backscattering in the microresonator by more than 30 dB. The method relies on controlling the scatterer position such that the intrinsic and scatterer-induced backpropagating fields destructively interfere. This technique is useful in microresonator applications where backscattering is currently limiting the performance of devices, such as ring-laser gyroscopes and dual frequency combs, which both suffer from injection locking. Moreover, these findings are of interest for integrated photonic circuits in which back reflections could negatively impact the stability of laser sources or other components.

scholarly journals Stability Analysis of an Explicit Integration Algorithm with 3D Viscoelastic Artificial Boundary Elements

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Shutao Li ◽  
Jingbo Liu ◽  
Xin Bao ◽  
Yifan Jia ◽  
Lan Xiao ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Near Field ◽  
Boundary Elements ◽  
Artificial Boundary ◽  
Explicit Integration ◽  
Integration Algorithm ◽  
Explicit Algorithm ◽  
Time Increment ◽  
The Stability ◽  
Explicit Integration Algorithm

Viscoelastic artificial boundary elements are one of the most commonly used artificial boundaries when solving dynamic soil-structure interactions or near-field wave propagation problems. However, due to the lack of clear and practical stability criteria for the explicit algorithm that considers the influence of viscoelastic artificial boundary elements, the determination of the stable time increment in such numerical analyses is still a challenge. In this study, we proposed a numerical stability analysis method for the explicit algorithm with a 3D viscoelastic artificial boundary element based on the idea of a subsystem. Through this method, the artificial boundary subsystem that controls the stability of the overall numerical system is determined, and the analytical solution for the stability condition of the explicit integration algorithm with 3D viscoelastic artificial boundary elements is obtained. On this basis, the maximum time increment for solving dynamic problems with viscoelastic artificial boundary elements can be determined.

scholarly journals Cry-wolf signals emerging from coevolutionary feedbacks in a tritrophic system

2015 ◽  
Vol 282 (1818) ◽  
pp. 20152169 ◽  
Author(s):  
Atsushi Yamauchi ◽  
Minus van Baalen ◽  
Yutaka Kobayashi ◽  
Junji Takabayashi ◽  
Kaori Shiojiri ◽  
...  
Keyword(s):  
Communication Systems ◽  
Feedback Loops ◽  
Tritrophic System ◽  
Evolution Of Communication ◽  
Herbivore Induced Plant Volatiles ◽  
Plant Signals ◽  
Selection For ◽  
The Stability ◽  
Plant Herbivore ◽  
Heavy Damage

For a communication system to be stable, senders should convey honest information. Providing dishonest information, however, can be advantageous to senders, which imposes a constraint on the evolution of communication systems. Beyond single populations and bitrophic systems, one may ask whether stable communication systems can evolve in multitrophic systems. Consider cross-species signalling where herbivore-induced plant volatiles (HIPVs) attract predators to reduce the damage from arthropod herbivores. Such plant signals may be honest and help predators to identify profitable prey/plant types via HIPV composition and to assess prey density via the amount of HIPVs. There could be selection for dishonest signals that attract predators for protection from possible future herbivory. Recently, we described a case in which plants release a fixed, high amount of HIPVs independent of herbivore load, adopting what we labelled a ‘cry-wolf’ strategy. To understand when such signals evolve, we model coevolutionary interactions between plants, herbivores and predators, and show that both ‘honest’ and ‘cry-wolf’ types can emerge, depending on the assumed plant–herbivore encounter rates and herbivore population density. It is suggested that the ‘cry-wolf’ strategy may have evolved to reduce the risk of heavy damage in the future. Our model suggests that eco-evolutionary feedback loops involving a third species may have important consequences for the stability of this outcome.

Landsliding caused by Pleistocene glacial lake ponding–an example from central British Columbia

1987 ◽  
Vol 24 (4) ◽  
pp. 656-663 ◽  
Author(s):  
N. Eyles ◽  
John J. Clague
Keyword(s):  
British Columbia ◽  
Debris Flows ◽  
Large Scale ◽  
Slope Failure ◽  
Glacial Lake ◽  
Fraser River ◽  
Stability Of Slopes ◽  
History Of ◽  
The Stability ◽  
Glacier Advance

Sections cut through the Quaternary sediment fill of the Fraser River valley in central British Columbia provide evidence for large-scale landsliding during Pleistocene time. Especially notable are thick, laterally extensive diamict beds, consisting mainly of Tertiary rock debris, that occur near the base of glaciolacustrine sequences. These beds were deposited by subaqueous debris flows during one or more periods of lake ponding when advancing Pleistocene glaciers blocked the ancestral Fraser River. The association of diamict beds and glaciolacustrine sediments deposited during periods of glacier advance may indicate a genetic link between slope failure and lake filling. These observations (1) demonstrate the adverse effects of high pore pressures on the stability of slopes underlain by poorly indurated Tertiary rocks and (2) extend the known history of landslides involving these rocks back into the Pleistocene. Key words: landslides, debris flows, Pleistocene, glacial lake.

scholarly journals Landslide and flood hazard index for mountain roads an example from the Stura di Demonte Valley, Italy

2000 ◽  
Vol 21 ◽  
Author(s):  
G. Barisone ◽  
A. Onori
Keyword(s):  
Debris Flows ◽  
Flood Hazard ◽  
Hazard Index ◽  
Thematic Map ◽  
The Road ◽  
Crossing Structures ◽  
Level Function ◽  
Short Time ◽  
Heavy Damage ◽  
Rock And Soil

Road alignments in mountainous areas are subject to heavy damage due to rockslides and floods. The rehabilitation and maintenance works that would be necessary to solve these problems are very costly. In this paper, the authors present methodology for obtaining, in relatively short time, a sufficiently detailed thematic map in which road alignment is subdivided into segments corresponding to different hazard degrees. As an example for such methodology, a 30 km long stretch of the road alignment in the Stura di Demonte Valley (Piedmont, Northwestern Italy) was chosen. The geomechanical characteristics of rock and soil in the area were obtained at the beginning. Major landslide phenomena (mostly rockfalls and debris flows) damaging the road alignment were located. A qualitative hazard index (Hi) was then calculated by taking into account such factors as affected road length, type and dimensions of the landslide, soil properties, and vegetation. Major hazards from rivers result from potential floods, which may overflow or erode road structures and destroy bridges and minor crossings. Firstly, the maximum discharge of rivers in the study area was calculated using various hydrological methods. Secondly, river expansion limits were evaluated. Historical data on past flood levels were considered during this process. During the high floods, malfunctioning of brides and other crossing structures can often have very serious consequences. The efficiency level of such structures, therefore was judged, taking their down-flowing section into consideration. For each structure, a comparison between estimated maximum river discharge and allowable discharge level (function of bridge and riverbed characteristics) determines the adequacy index (Ai). Results of analysis of both flood and landslide hazard were then synthesised in the final hazard map, which shows with simple graphic symbols and an intuitive colour range (in order to allow easy consultation by non-experts), the most important hazard factors, pertinent protection works, and resulting hazard degrees for roads, bridges, and other structures.

scholarly journals Wildfire Impacts on Slope Stability Triggering in Mountain Areas

Geosciences ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 417 ◽  
Author(s):  
Abbate ◽  
Longoni ◽  
Ivanov ◽  
Papini
Keyword(s):  
Slope Stability ◽  
Debris Flows ◽  
Degree Of Saturation ◽  
Critical Conditions ◽  
Vegetation Coverage ◽  
Large Variability ◽  
Stability Of Slopes ◽  
Wildfire Effects ◽  
The Stability

Landslides over steep slopes, floods along rivers plains and debris flows across valleys are hydrogeological phenomena typical for mountain regions. Such events are generally triggered by rainfall, which can have large variability in terms of both its intensity and volume. Furthermore, terrain predisposition and the presence of some disturbances, such as wildfires, can have an adverse effect on the potential risk. Modelling the complex interaction between these components is not a simple task and cannot always be carried out using instability thresholds that only take into account the characteristics of the rainfall events. In some particular cases, external factors can modify the existing delicate equilibrium on the basis of which stability thresholds are defined. In particular, events such as wildfires can cause the removal of vegetation coverage and the modification of the soil terrain properties. Therefore, wildfires can effectively reduce the infiltration capacity of the terrain and modify evapotranspiration. As a result, key factors for slope stability, such as the trend of the degree of saturation of the terrain, can be strongly modified. Thus, studying the role of wildfire effects on the terrain’s hydrological balance is fundamental to establish the critical conditions that can trigger potential slope failures (i.e., shallow landslides and possible subsequent debris flows). In this work, we investigate the consequences of wildfire on the stability of slopes through a hydrological model that takes into account the wildfire effects and compare the results to the current stability thresholds. Two case studies in the Ardenno (IT) and Ronco sopra Ascona (CH) municipalities were chosen for model testing. The aim of this paper is to propose a quantitative analysis of the two cases studies, taking into account the role of fire in the slope stability assessment. The results indicate how the post-fire circumstances strongly modify the ability of the terrain to absorb rainfall water. This effect results in a persistently drier terrain until a corner point is reached, after which the stability of the slope could be undermined by a rainfall event of negligible intensity.

scholarly journals Influences of hydrological and hydrogeological conditions on debris flows in peri-vesuvian hillslopes

2002 ◽  
Vol 2 (1/2) ◽  
pp. 27-35 ◽  
Author(s):  
P. De Vita ◽  
V. Piscopo
Keyword(s):  
Hydraulic Conductivity ◽  
Debris Flows ◽  
Pattern Analysis ◽  
Rainfall Pattern ◽  
Soil Stability ◽  
Strong Variation ◽  
Hydraulic Flow ◽  
Water Tables ◽  
The Stability ◽  
Pyroclastic Soil

Abstract. The paper illustrates some results of research carried out to assess factors triggering debris flows which involve the pyroclastic overburdens covering carbonate mountains around Vesuvius. The aims of the research were to reconstruct a relationship between rainfall and debris flow occurrence and to highlight empirical hydrological thresholds through rainfall pattern analysis. The research was also aimed at investigating hydrogeological features of a pyroclastic cover-carbonate bedrock system to analyse factors inducing temporary hydraulic flow, critical for pyroclastic soil stability. The results of research are the following: i) rainfall pattern highlights empirical hydrological thresholds that differentiate the Lattari and Salerno Mountains from the Sarno Mountains; ii) in some sample areas of the Sarno Mountains close to the trigger zones of the landslides of May 1998 strong variation in hydraulic conductivity has been found in the first few meters below the surface; iii) these permeability variations would seem to justify temporary perched water tables that might affect the stability of the pyroclastic mantle.

Genre Diversity and the State's Hegemony over Free-to-Air Television in New Zealand

2004 ◽  
Vol 112 (1) ◽  
pp. 201-219
Author(s):  
Brennon Wood
Keyword(s):  
New Zealand ◽  
Public Service ◽  
General Trend ◽  
Formal Structure ◽  
Convergence Hypothesis ◽  
The Stability

The commercialisation of New Zealand television in the 1990s has provoked debate between those who hold that markets increase diversity and those who believe that competition produces homogeneity. Focusing on the formal structure of program types, this article uses a range of statistics to assess historical shifts in the entropic breadth of genres, the stability of this mix, shifts in modality and variations by channel. In keeping with the convergence hypothesis, the findings indicate a general trend towards stabilisation, domination by entertainment and increased hybridity. However, entropy has remained consistently high. Moreover, entertainment declined and information rose throughout the 1990s. These unexpected results are an outcome of market partitioning established by state television in the 1970s and 1980s. Rather than either the advent of neo-liberal variety or a decline of public service diversity, this analysis emphasises the state's persistent hegemony over the free-to-air market.

SURFACE PROCESS AND FLUVIAL LANDFORM RESPONSE TO THE MS 8.0 WENCHUAN EARTHQUAKE, LONGMEN SHAN, CHINA

2013 ◽  
Vol 07 (05) ◽  
pp. 1350033 ◽  
Author(s):  
Y. LI ◽  
Z. K. YAN ◽  
R. J. ZHOU ◽  
L. SVIRCHEV ◽  
H. B. LI ◽  
...  
Keyword(s):  
Wenchuan Earthquake ◽  
Debris Flows ◽  
Slip Surface ◽  
River Channel ◽  
Coseismic Deformation ◽  
Mountain Range ◽  
River Channels ◽  
Surface Ruptures ◽  
To Come ◽  
Landslides And Debris Flows

The MS 8.0 Wenchuan earthquake of May 12, 2008, in the Longmen Shan mountain range area in China, led to two roughly parallel NE-trending thrust and strike-slip surface ruptures of the Beichuan, Pengguan, and the Xiaoyudong faults. Coseismic deformation changed the topographical gradient and produced massive landslides and debris flows, causing a corresponding response of the fluvial landforms. In this paper, based on data regarding the surface ruptures and changes to the topography and drainage resulting from the earthquake, the influence of the thrusting and strike-slipping on fluvial landforms and drainage are integrated and analyzed. The results are shown for the following five main aspects: (1) the strike-slipping driven by the earthquake caused the formation of new tectonic diversion points of river channels; (2) the thrusting driven by the earthquake caused the formation of new tectonic slope-break points in the river channel; (3) the strikes of the faults activated by the earthquake controlled the river channel direction; (4) the uplifting driven by the earthquake led to changes of riverbed gradient profiles and their base levels; and (5) exceptionally heavy rainfall after the earthquake initiated landslides, debris flows and floods, and will continue to be a hazard for several decades to come.

Hazard Assessment of Debris Flow Based on the TFSE: A Case along Jinsha River close to the Jinsha Dam Site in China

2013 ◽  
Vol 405-408 ◽  
pp. 2358-2363
Author(s):  
Bo Shan ◽  
Qing Wang ◽  
Jian Ping Chen ◽  
Hui Xiong
Keyword(s):  
Debris Flow ◽  
Hazard Assessment ◽  
Debris Flows ◽  
Human Life ◽  
Fuzzy Synthetic Evaluation ◽  
Related Factors ◽  
Jinsha River ◽  
Design Storm ◽  
The Stability ◽  
Major Factors

Debris flows are common natural hazards in China. The outbreak of debris flows in reservoir region not only affects the stability of the hydropower stations dam, but also threatens the safety of human life and their property. Therefore, hazard assessment and protection of debris flows close to the dam are necessary and important. In this paper, SPOT5 remote sensing images and DEM model and scene investigation are introduced to acquire the characteristics of debris flow gullies. Ten debris flow occurrence related factors were selected. Then, on the basic of analyzing the relationship of the major factors and fuzzification of debris flow hazard degree, the model of two-stage fuzzy synthetic evaluation (TFSE) was established for hazard assessment. The debris flow risk under different designed rainstorm frequency was calculated. By the evaluation results, we can know that with the design storm intensity increases, the risk of debris flow increases, which is consistent with the actual situation.

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