scholarly journals Seismic signature of the deadly snow avalanche of January 18, 2017, at Rigopiano (Italy)

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Thomas Braun ◽  
Barbara Frigo ◽  
Bernardino Chiaia ◽  
Perry Bartelt ◽  
Daniela Famiani ◽  
...  
Keyword(s):  
Motion Analysis ◽  
Particle Motion ◽  
Mass Movement ◽  
Maximum Velocity ◽  
Seismic Source ◽  
Weather Conditions ◽  
Synthetic Seismograms ◽  
Snow Avalanche ◽  
Time Range ◽  
Snow Avalanches

Abstract Most snow avalanches occur unobserved, which becomes particularly dramatic when human lives are involved. Seismological observations can be helpful to unravel time and dynamics of unseen events, like the deadly avalanche of January 18, 2017, that hit a Resort-hotel at Rigopiano in the Abruzzi (Italy). Particle motion analysis and spectrograms from data recorded by a close seismic broadband station, calculation of synthetic seismograms, as well as simulation of the flow, allowed us to construct the dynamics of the snow avalanche that buried alive 40 people, killing 29. Due to the bad weather conditions, no visual observation was made, thus making it impossible to determine the exact moment of the avalanche and to report necessary observations of the dramatic event. On-site inspections revealed that the hotel was horizontally cut by shear forces and dislocated by 48 m in 70°N direction, once the increasing avalanche pressure exceeded the structural shear strength of the building. Within an eligible 24 min time range of the avalanche, we found three weak seismic transients, starting at 15:42:38 UTC, recorded by the nearest operating station GIGS located in the Gran Sasso underground laboratory approximately 17 km away. Particle motion analysis of the strongest seismic avalanche signal, as well as of the synthetic seismograms match best when assuming a single force seismic source, attacking in direction of 120°N. Simulation of the avalanche dynamics—calculated by using a 2D rapid mass movement simulator—indicates that the seismic signals were rather generated as the avalanche flowed through a narrow and twisting canyon directly above the hotel. Once the avalanche enters the canyon it is travelling at maximum velocity (37 m/s) and is twice strongly deflected by the rock sidewalls. These impacts created a distinct linearly polarized seismic “avalanche transient”s that can be used to time the destruction of the hotel. Our results demonstrate that seismic recordings combined with simulations of mass movements are indispensable to remotely monitor snow avalanches.

The use of seismic ground particle motion for snow avalanche release area identification

2021 ◽  
Author(s):  
Pere Roig Lafon ◽  
Emma Suriñach ◽  
Mar Tapia
Keyword(s):  
Success Rate ◽  
Particle Motion ◽  
Seismic Data ◽  
Signal Amplitude ◽  
Seismic Signal ◽  
Snow Avalanche ◽  
3D Seismic ◽  
Snow Avalanches ◽  
Release Area ◽  
Back Azimuth

<p>Knowledge of the snow avalanche release area is key information in snow avalanche studies. However, it is not easy to obtain from a remote location. The study of the seismic vibrations produced in the initial stages of the snow avalanche, makes possible to identify their origin and to link them to the starting area of the snow avalanche. We developed a methodology for this purpose, applied to seismic data acquired from a 3D seismic station (2Hz eigenfrequency) placed at Cavern A in Vallée de la Sionne experimental site (VDLS, WSL-SLF), deployed in 2013 by UB-RISKNAT. This is the closest position to the snow avalanche release areas, at 700 m to the farthest point. We focus on spontaneous triggered snow avalanches to achieve better signal-to-noise ratio and to be more realistic on its application.</p><p>For the isolation of the Signal Onset (SON) section of seismic data, which corresponds to those vibrations produced by the initial stage of the snow avalanche, we use the STA/LTA ratios and seismic signal amplitude, common methodologies in seismology. The STA/LTA is used for the identification of the first vibrations produced by the movement of the snow mass and the seismic signal amplitude thresholds for the identification of the end of the SON section -when the snow avalanche front reaches the seismic sensor position-. The 3D seismic data [ZNE components] of the SON section were processed in time windows. The study of polarization of the particle motion to obtain the direction of the back-azimuth of the signal (Vidale, 1986; Jurckevicks, 1988) was carried out for each time window of the seismic signal. The accumulation of back-azimuth directions for the entire SON section is related to the origin of the vibrations and, by extension, to the snow avalanche release area.</p><p>The entire algorithm has been automated. In its application on all the trigger activations at VDLS since 2015 until 2020, it was achieved a success rate of 78% on snow avalanche release area identification. In addition, we defined an algorithm based on STA/LTA ratio to select the snow avalanches from other seismic events, used with a success rate of 95%.</p><p>We present the application of our method in a case study, a large spontaneous snow avalanche released on 16th February 2018 at VDLS. The snow avalanche had two main release areas, clearly identified in photos of the site. The two developed fronts can be recognized in the seismic data. The directions to the release areas from Cavern A position can be identified using the presented method. Also, more interpretations can be done on the downhill snow avalanche path.</p>

scholarly journals Snow Avalanche Assessment in Mass Movement-Prone Areas: Results from Climate Extremization in Relationship with Environmental Risk Reduction in the Prati di Tivo Area (Gran Sasso Massif, Central Italy)

Land ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1176
Author(s):  
Massimiliano Fazzini ◽  
Marco Cordeschi ◽  
Cristiano Carabella ◽  
Giorgio Paglia ◽  
Gianluca Esposito ◽  
...  
Keyword(s):  
Risk Mitigation ◽  
Mass Movement ◽  
Central Italy ◽  
Scientific Basis ◽  
Snow Avalanche ◽  
High Mountain ◽  
Mass Movements ◽  
Snow Avalanches ◽  
Massif Central ◽  
Mountain Environments

Mass movements processes (i.e., landslides and snow avalanches) play an important role in landscape evolution and largely affect high mountain environments worldwide and in Italy. The increase in temperatures, the irregularity of intense weather events, and several heavy snowfall events increased mass movements’ occurrence, especially in mountain regions with a high impact on settlements, infrastructures, and well-developed tourist facilities. In detail, the Prati di Tivo area, located on the northern slope of the Gran Sasso Massif (Central Italy), has been widely affected by mass movement phenomena. Following some recent damaging snow avalanches, a risk mitigation protocol has been activated to develop mitigation activities and land use policies. The main goal was to perform a multidisciplinary analysis of detailed climatic and geomorphological analysis, integrated with Geographic Information System (GIS) processing, to advance snow avalanche hazard assessment methodologies in mass movement-prone areas. Furthermore, this work could represent an operative tool for any geomorphological hazard studies in high mountainous environments, readily available to interested stakeholders. It could also provide a scientific basis for implementing sustainable territorial planning, emergency management, and loss-reduction measures.

Impacts of land-cover changes on dendrogeomorphic reconstructions of snow avalanches: Insights from the Queyras massif (French Alps)

2020 ◽  
Author(s):  
Adrien Favillier ◽  
Robin Mainieri ◽  
Jérôme Lopez-Saez ◽  
Mélanie Saulnier ◽  
Nicolas Eckert ◽  
...  
Keyword(s):  
Global Warming ◽  
Snow Cover ◽  
Tree Ring ◽  
Environmental Changes ◽  
Mass Movement ◽  
Sudden Change ◽  
Snow Avalanche ◽  
High Mountain ◽  
Snow Avalanches ◽  
French Alps

<p>In the course of the 20th century, high-mountain regions, such as the Alps, have experienced a significant warming with temperature increase twice as much as the global average. Such warming strongly alters the cryosphere components. It induces, for example, a shift from solid to liquid precipitation, more frequent and more intense snowmelt phases or a strong decrease in the amount and duration of snow cover, especially at the location of the snow-rain transition. Such changes in snow cover characteristics are expected to induce changes in spontaneous avalanche activity.</p><p>On forested stands, dendrogeomorphic analyses provide long and continuous chronologies of snow avalanche events and can thus contribute to the detection of trends potentially related to climate change. However, the non-stationarities found in tree-ring based chronologies of snow avalanches may also be related to socio-environmental changes. In this context, based on the latest the latest developments in dendrogeomorphology, we reconstructed the snow avalanche activity for 6 contiguous paths located in the Grand Bois de Souliers slope (Queyras massif, French Alps) with the aim to :</p><ol><li>Detect and illustrate such confounding effects;</li> <li>Disentangle the trends inherent to tree-ring approaches from real fluctuations in avalanche activity.</li> </ol><p>The resulting reconstruction covers the period 1750-2016 and evidences two clearly different trends: on the three southern avalanche paths, a sharp increase in the frequency of reconstructed events is observed since the 1970s. The distribution of tree ages, in combination with old topographic maps, allows an attribution of this non-stationarity to the destruction of a large part of the forest stand in the 1910-20s, presumably related to a devastating avalanche event. This extreme event induced a sudden change in the capability of newly colonizing trees to yield dendrogeomorphic records as information on previous or subsequent events has been removed. By contrast, on the three northern paths, snow avalanche activity is truly characterized by a strong reduction since the 1930s related to the progressive afforestation of the paths since the mid-18<sup>th</sup> century and to the colonization of the release areas since World War 2. Even if we cannot rule out the possibility that global warming may have played a certain, yet likely minor, role in the evolution of these avalanche-forest ecosystem, we conclude that the contrasted evolutions observed between the avalanche paths can, above all, be explained by socio-environmental factors (e.g., forest and grazing management) during the 18<sup>th</sup> century that have gained in importance by the rural exodus and the abatement of pastoral practices during the 20<sup>th</sup> century. In that sense, our results evidence quite clearly the crucial need for future studies aimed at detecting changes in mass-movement activity from tree-ring analyses to systematically interpret trends in activity considering interrelations between forest evolution, global warming, social practices and process activity itself.</p>

scholarly journals Numerical modeling of snow avalanche dynamics based on the Material Point Method

2020 ◽  
Author(s):  
Xingyue Li ◽  
Betty Sovilla ◽  
Stephanie Wang ◽  
Chenfanfu Jiang ◽  
Johan Gaume
Keyword(s):  
Numerical Modeling ◽  
Material Point Method ◽  
Maximum Velocity ◽  
Flow Regimes ◽  
Material Point ◽  
Point Method ◽  
Surface Shape ◽  
Snow Avalanche ◽  
Snow Avalanches ◽  
Avalanche Dynamics

<p>Snow avalanches are one of the most dangerous and catastrophic hazards in mountainous regions, which cause fatalities and property losses. Understanding the dynamics of snow avalanches is essential for designing safe and optimised mitigation measures. This study presents numerical modeling of snow avalanche dynamics, based on the Material Point Method (MPM) and an elastoplastic constitutive model for porous cohesive materials. MPM is a hybrid Eulerian-Lagrangian numerical method, which can simulate processes with large deformation, collisions and fractures. The elastoplastic model consists of an ellipsoid yield surface, a hardening law, and an associative flow rule. It enables us to capture the mixed-mode failure of snow including tensile, shear and compressive failure. Both ideal and real terrains are modeled in our study. By varying the properties of snow on the ideal slope, the model can reproduce four typical reported flow regimes, namely, cold shear, warm shear, warm plug and slab sliding regimes. In addition, surges and roll-waves are observed especially for flows in the transition from cold shear to warm shear regimes. The evolution of the avalanche front, the free surface shape and the velocity vertical profile show distinct characteristics for the different flow regimes. In addition to the snow properties, slope angle and path length are changed to investigate their effects on the maximum velocity, the run-out distance and the avalanche deposit height. The relation between the maximum velocity and the run-out distance obtained from our MPM simulations is analyzed along with data collected from literature. Furthermore, we benchmark the MPM model by simulating snow avalanches on real terrain. The evolution of the avalanche front position and velocity from the MPM simulations are quantitatively compared with the measurement data from past studies.</p>

Detection of P-S travel time for low SNR event by particle motion analysis

2021 ◽  
Author(s):  
Jingyi Sun ◽  
Yusuke Mukuhira ◽  
Takayuki Nagata ◽  
Taku Nonomura ◽  
Hirokazu Moriya ◽  
...  
Keyword(s):  
Travel Time ◽  
Motion Analysis ◽  
Particle Motion ◽  
Low Snr

scholarly journals The mechanical origin of snow avalanche dynamics and flow regime transitions

2020 ◽  
Author(s):  
Xingyue Li ◽  
Betty Sovilla ◽  
Chenfanfu Jiang ◽  
Johan Gaume
Keyword(s):  
Flow Velocity ◽  
Alpha Angle ◽  
Maximum Flow ◽  
Flow Regimes ◽  
Snow Avalanche ◽  
Snow Avalanches ◽  
Deposition Zone ◽  
Avalanche Dynamics ◽  
Maximum Flow Velocity ◽  
Deposit Height

Abstract. Snow avalanches cause fatalities and economic damages. Key to their mitigation entails the understanding of snow avalanche dynamics. This study investigates the dynamic behaviors of snow avalanches, using the Material Point Method (MPM) and an elastoplastic constitutive law for porous cohesive materials. By virtue of the hybrid Eulerian-Lagrangian nature of MPM, we can handle processes involving large deformations, collisions and fractures. Meanwhile, the elastoplastic model enables us to capture the mixed-mode failure of snow, including tensile, shear and compressive failure. Using the proposed numerical approach, distinct behaviors of snow avalanches, from fluid-like to solid-like, are examined with varied snow mechanical properties. In particular, four flow regimes reported from real observations are identified, namely, cold dense, warm shear, warm plug and sliding slab regimes. Moreover, notable surges and roll-waves are observed peculiarly for flows in transition from cold dense to warm shear regimes. Each of the flow regimes shows unique flow characteristics in terms of the evolution of the avalanche front, the free surface shape, and the vertical velocity profile. We further explore the influence of slope geometry on the behaviors of snow avalanches, including the effect of slope angle and path length on the maximum flow velocity, the $\\alpha$ angle and the deposit height. Unified trends are obtained between the normalized maximum flow velocity and the scaled $\\alpha$ angle as well as the scaled deposit height, reflecting analogous rules with different geometry conditions of the slope. It is found the maximum flow velocity is mainly controlled by the friction between the bed and the flow, the geometry of the slope, and the snow properties. In addition to the flow behavior before reaching the deposition zone, which has long been regarded as the key factor governing the $\\alpha$ angle, we reveal the crucial effect of the stopping behavior in the deposition zone. Furthermore, our MPM model is benchmarked with simulations of real snow avalanches. The evolution of the avalanche front position and velocity from the MPM modeling shows reasonable agreement with the measurement data from literature. The MPM approach serves as a novel and promising tool to offer systematic and quantitative analysis for mitigation of gravitational hazards like snow avalanches.

A numerical approach for simulating two-dimensional dense-snow avalanches in global coordinate systems

2021 ◽  
Author(s):  
Daniel Zugliani ◽  
Giorgio Rosatti ◽  
Stefania Sansone
Keyword(s):  
Coordinate System ◽  
Finite Volume ◽  
Reference System ◽  
Source Term ◽  
Numerical Approach ◽  
The Other ◽  
Snow Avalanche ◽  
Two Dimensional ◽  
Snow Avalanches ◽  
Avalanche Models

<p>Snow avalanche models are commonly based on a continuum fluid scheme, on the assumption of shallow flow in the direction normal to the bed, on a depth-averaged description of the flow quantities and on different assumptions concerning the velocity profile, the friction law, and the pressure in the flow direction (see Bartelt et al, 1999, Barbolini et al., 2000, for an overview). The coordinate reference system is commonly local, i.e., for each point of the domain, one axis is normal to the bed while the other two axes lay in a tangent plane. When the bed is vertical and the flow is not aligned with the steepest direction (e.g., in case of a side wall), the flow depth is no longer defined considering the normal direction and the model based on the local coordinate system is no longer valid. In near-vertical conditions, numerical problems can be expected.</p><p>Another critical point, for numerical models based on finite volume schemes and Godunov fluxes, is the accurate treatment of the source term in case of no-motion conditions (persistence, starting and stopping of the flow) due to the presence of velocity-independent, Coulomb-type terms in the bed shear stress. </p><p>In this work, we provide a numerical approach for a Voellmy-fluid based model, able to overcome the limits depicted above, to accurately simulate analytical solutions and to give reliable solutions in other cases (Zugliani & Rosatti, 2021). Firstly, differently from the other literature models, the chosen coordinate reference system is global (an axis opposite the gravity vector and the other two orthogonal axes lay in the horizontal plane) and therefore, the relevant mass and momentum equations have been derived accordingly. Secondly, these equations have been discretized by using a finite volume method on a Cartesian square grid where the Godunov fluxes has been evaluated by mean of a modified DOT scheme (Zugliani & Rosatti, 2016) while source terms in conditions of motion have been discretized by using an implicit operator-splitting technique. Finally, a specific algorithm has been derived to deal with the source term to determine the no-motion conditions.  Several test cases assess the capabilities of the proposed approach.</p><p> </p><p><strong>References:</strong></p><p>Barbolini, M., Gruber, U., Keylock, C.J., Naaim, M., Savi, F. (2000), <em>Application of statistical and hydraulic-continuum dense-snow avalanche models to five real European sites.</em> Cold Regions Science and Tech. 31, 133–149.</p><p>Bartelt, P., Salm, B., Gruber, U. (1999), <em>Calculating dense-snow avalanche runout using a voellmy-fluid model with active/passive longitudinal straining.</em> Journal of Glaciology 45, 242-254.</p><p>Zugliani D., Rosatti G. (2021), <em>Accurate modeling of two-dimensional dense snow avalanches in global coordinate system: the TRENT2D<sup>❄</sup> approach. </em>Paper under review.</p><p>Zugliani, D., Rosatti, G. (2016), <em>A new Osher Riemann solver for shallow water flow over fixed or mobile bed</em>, Proceedings of the 4th European Congress of the IAHR, pp. 707–713.</p>

scholarly journals Analysis of Wave Energy Conversion with Dynamic Systems Theory

2019 ◽  
Vol 103 ◽  
pp. 02003
Author(s):  
Sorin Ciortan ◽  
Eugen Rusu
Keyword(s):  
Dynamic System ◽  
Energy Conversion ◽  
Wave Energy ◽  
Prediction Models ◽  
Weather Conditions ◽  
Point Of View ◽  
The Black Sea ◽  
Time Range ◽  
Wave Energy Conversion ◽  
Dynamic System Theory

In wave energy conversion one of the most important steps is building scenarios about long term efficiency, taking into account that several factors are involved. Based on the assumption that actually the weather conditions show important modifications year by year, analyses of wave power evolution during the exploitation time range must rely on both prediction models and on several options for the conversion device. From this point of view, the wave energy conversion process can be considered a dynamic system. The dynamic system theory based methodology approach systems behaviour through relationships between systems components. Comparing to usual scientific approaches, which try to decompose the analyzed system, this methodology offers a view of entire system behaviour The paper presents a method for building scenarios of wave energy conversion, in the nearshore of the Black Sea, based on a model which includes also forecasts of the weather influence.

scholarly journals Scale Modeling of Snow–Avalanche Impact on Structures

1980 ◽  
Vol 26 (94) ◽  
pp. 189-196
Author(s):  
T. E. Lang ◽  
J.D. Dent
Keyword(s):  
Froude Number ◽  
Computer Modeling ◽  
Snow Avalanche ◽  
Small Scale ◽  
Snow Avalanches ◽  
Scale Modeling ◽  
Impact Processes ◽  
Model Fluid ◽  
Impact Predictions

AbstractSmall–scale modeling of flow and impact of snow avalanches is demonstrated to be both feasible and accurate. Geometric, kinematic, and force variables are scaled correctly under equivalence of Froude number between prototype and model using sifted snow as the model fluid. Physical and computer–simulated impact processes show correspondence, so that computer modeling is demonstrated to be a viable tool in flow and impact predictions.

scholarly journals Rockfall induced seismic signals: case study in Montserrat, Catalonia

2008 ◽  
Vol 8 (4) ◽  
pp. 805-812 ◽  
Author(s):  
I. Vilajosana ◽  
E. Suriñach ◽  
A. Abellán ◽  
G. Khazaradze ◽  
D. Garcia ◽  
...  
Keyword(s):  
Particle Motion ◽  
Mass Movement ◽  
Seismic Energy ◽  
Quantitative Information ◽  
Volume Estimation ◽  
Seismic Signals ◽  
Energy Estimation ◽  
Time Frequency ◽  
On The Road ◽  
The Impact

Abstract. After a rockfall event, a usual post event survey includes qualitative volume estimation, trajectory mapping and determination of departing zones. However, quantitative measurements are not usually made. Additional relevant quantitative information could be useful in determining the spatial occurrence of rockfall events and help us in quantifying their size. Seismic measurements could be suitable for detection purposes since they are non invasive methods and are relatively inexpensive. Moreover, seismic techniques could provide important information on rockfall size and location of impacts. On 14 February 2007 the Avalanche Group of the University of Barcelona obtained the seismic data generated by an artificially triggered rockfall event at the Montserrat massif (near Barcelona, Spain) carried out in order to purge a slope. Two 3 component seismic stations were deployed in the area about 200 m from the explosion point that triggered the rockfall. Seismic signals and video images were simultaneously obtained. The initial volume of the rockfall was estimated to be 75 m3 by laser scanner data analysis. After the explosion, dozens of boulders ranging from 10−4 to 5 m3 in volume impacted on the ground at different locations. The blocks fell down onto a terrace, 120 m below the release zone. The impact generated a small continuous mass movement composed of a mixture of rocks, sand and dust that ran down the slope and impacted on the road 60 m below. Time, time-frequency evolution and particle motion analysis of the seismic records and seismic energy estimation were performed. The results are as follows: 1 – A rockfall event generates seismic signals with specific characteristics in the time domain; 2 – the seismic signals generated by the mass movement show a time-frequency evolution different from that of other seismogenic sources (e.g. earthquakes, explosions or a single rock impact). This feature could be used for detection purposes; 3 – particle motion plot analysis shows that the procedure to locate the rock impact using two stations is feasible; 4 – The feasibility and validity of seismic methods for the detection of rockfall events, their localization and size determination are comfirmed.

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