High‐resolution radar measurements of snow avalanches

Vriend, Nathalie; McElwaine, J. N.; Sovilla, Betty; Keylock, Christopher J.; Ash, Matthew; Brennan, Paul V.

doi:10.1002/grl.50134

Cited by 42 publications

(40 citation statements)

References 16 publications

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“…A detailed description of the measurement principle and the radar design can be found in Ash et al [2010Ash et al [ , 2011. The first published results were based on findings with GEODAR Mark 1 [Vriend et al, 2013], whereas the data described here were obtained with the GEODAR Mark 3 system. This system has a higher pulse repetition rate, which increases the measurement frequency, and has a better pulse-to-pulse coherency due to the use of phase-locked signals which results in a stable phase between each pulses and each antenna.…”

Section: Geodarmentioning

confidence: 99%

“…We use an MTI high-pass filter of 151 samples in length, with a normalized cutoff frequency of 0.12 generated by the function fir2.m in the OCTAVE signal processing package. In contrast to Vriend et al [2013], which applied a time domain filter with coefficients [1, −1] as the difference between only two adjacent pulses, the filter used here has a flatter passband response with a sharper cutoff and gives clearer results.…”

Section: Dynamics Of Surges In Snow Avalanchesmentioning

confidence: 99%

“…They can correspond to features at different lateral locations moving with different speeds (Figure 1c), or they can overtake each other at the same lateral location (Figure 1e). GEODAR cannot distinguish between both cases on its own [Vriend et al, 2013]. Nevertheless, the small powder cloud in the first part of the avalanche track ( Figure 5, bottom) allows a degree of visual "calibration" and later in the avalanche path the channeled topography limits the lateral extend of the flow.…”

Section: Dynamics Of Surges In Snow Avalanchesmentioning

confidence: 99%

“…The FMCW radars are useful in detecting small-scale flow structures that cannot be distinguished in the GEODAR signal since they resolve through the flow rather than across the flow. [Vriend et al, 2013].…”

Section: Upward Looking Fmcw Radarmentioning

confidence: 99%

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The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

Köhler¹,

McElwaine

Sovilla³

et al. 2016

JGR Earth Surface

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Five avalanches were artificially released at the Vallée de la Sionne test site in the west of Switzerland on 3 February 2015 and recorded by the GEOphysical flow dynamics using pulsed Doppler radAR Mark 3 radar system. The radar beam penetrates the dilute powder cloud and measures reflections from the underlying denser avalanche features allowing the tracking of the flow at 111 Hz with 0.75 m downslope resolution. The data show that the avalanches contain many internal surges. The large or “major” surges originate from the secondary release of slabs. These slabs can each contain more mass than the initial release, and thus can greatly affect the flow dynamics, by unevenly distributing the mass. The small or “minor” surges appear to be a roll wave‐like instability, and these can greatly influence the front dynamics as they can repeatedly overtake the leading edge. We analyzed the friction acting on the fronts of minor surges using a Voellmy‐like, simple one‐dimensional model with frictional resistance and velocity‐squared drag. This model fits the data of the overall velocity, but it cannot capture the dynamics and especially the slowing of the minor surges, which requires dramatically varying effective friction. Our findings suggest that current avalanche models based on Voellmy‐like friction laws do not accurately describe the physics of the intermittent frontal region of large mixed avalanches. We suggest that these data can only be explained by changes in the snow surface, such as the entrainment of the upper snow layers and the smoothing by earlier flow fronts.

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Section: Geodarmentioning

confidence: 99%

Section: Dynamics Of Surges In Snow Avalanchesmentioning

confidence: 99%

Section: Dynamics Of Surges In Snow Avalanchesmentioning

confidence: 99%

Section: Upward Looking Fmcw Radarmentioning

confidence: 99%

See 2 more Smart Citations

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

Köhler¹,

McElwaine

Sovilla³

et al. 2016

JGR Earth Surface

Self Cite

View full text Add to dashboard Cite

show abstract

“…Furthermore, a Frequency Modulated Continuous Wave Phased Array radar (henceforth referred to as the GEODAR radar) is located at the shelter (Vriend et al, 2013;Ash et al, 2014). It can track the avalanche over the whole slope with a downslope spatial resolution of 0.75 m, and gives information on avalanche position, velocity and size.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Evaluation of a snow avalanche possibly triggered by a local earthquake at Vallée de la Sionne, Switzerland

Pérez-Guillén

Tapia

Furdada

et al. 2014

Cold Regions Science and Technology

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Please cite this article as: Pérez-Guillén, C., Tapia, M., Furdada, G., Suriñach, E., McElwaine, J.N., Steinkogler, W., Hiller, M., Evaluation of a snow avalanche possibly triggered by a local earthquake at Vallée de la Sionne, Switzerland, Cold Regions Science and Technology (2014), doi: 10.1016/j.coldregions.2014 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractSnow avalanches are moving sources of infrasonic and seismic energy. They can be triggered by many different mechanisms that include the shaking produced by earthquakes. The forces induced by an earthquake can cause an increase in the load down the slope and can also decrease the shear strength and both effects can cause the release of an avalanche. This phenomenon represents an important hazard associated with earthquakes in snow-covered mountain areas with high seismicity.On 6 December 2010 a snow avalanche was released at the experimental site of Vallée de la Sionne (VDLS) in Switzerland seconds after a local earthquake of magnitude A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2 M L 3.1 with the hypocenter in France, approximately 43 km from the avalanche starting zone. The seismic and infrasound signals generated by the earthquake and the snow avalanche were recorded by an array of sensors installed at VDLS. This paper analyses these data and shows that the avalanche was possibly triggered by the earthquake. This analysis also allows us to determine the characteristics of the avalanche (type and path).The infrasound data shows that the time of the avalanche release coincided with the arrival of the seismic waves of the earthquake. We calculate the values of the ground vibration parameters (PGD, PGV, PGA, PSA, I a and TD) measured at the release area of the avalanche and compare them with those of two other earthquakes that did not trigger an avalanche. To evaluate the influence of the snowpack stratigraphy with the effectiveness of the earthquakes to trigger an avalanche, we simulate the snow cover using the one-dimensional snow cover model SNOWPACK. The weather and snow cover conditions of the days on which these events occurred are compared and used to evaluate the snowpack stability and the consequent likelihood of avalanche activity. The snowpack stability is the primary factor that determines whether an avalanche may be triggered by minor earthquakes. We conclude that when the snowpack is only marginally stable then the displacement caused by even a small earthquake could be enough to trigger an avalanche. Furthermore, the analysis of the other two, even stronger...

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Calculating the velocity of a fast‐moving snow avalanche using an infrasound array

Havens

Marshall

Johnson

et al. 2014

Geophysical Research Letters

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On 19 January 2012, a large D3 avalanche (approximately 103 t) was recorded with an infrasound array ideally situated for observing the avalanche velocity. The avalanche crossed Highway 21 in Central Idaho during the largest avalanche cycle in the 15 years of recorded history and deposited approximately 8 m of snow on the roadway. Possible source locations along the avalanche path were estimated at 0.5 s intervals and were used to calculate the avalanche velocity during the 64 s event. Approximately 10 s prior to the main avalanche signal, a small infrasound signal originated from the direction of the start zone. We infer this to be the initial snow pack failure, a precursory signal to the impending avalanche. The avalanche accelerated to a maximum velocity of 35.9 ± 7.6m s−1 within 30 s before impacting the highway. We present a new technique to obtain high spatial and temporal resolution velocity estimates not previously demonstrated with infrasound for avalanches and other mass wasting events.

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High‐resolution radar measurements of snow avalanches

Cited by 42 publications

References 16 publications

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

The dynamics of surges in the 3 February 2015 avalanches in Vallée de la Sionne

Evaluation of a snow avalanche possibly triggered by a local earthquake at Vallée de la Sionne, Switzerland

Calculating the velocity of a fast‐moving snow avalanche using an infrasound array

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