Item: DRY-TO-WET TRANSITIONAL AVALANCHES: INFERENCE MADE USING INFRA SOUND SURVEILLANCE
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Title: DRY-TO-WET TRANSITIONAL AVALANCHES: INFERENCE MADE USING INFRA SOUND SURVEILLANCE
Proceedings: Proceedings, International Snow Science Workshop, Whistler, BC, Canada, 2026
Authors:
- Jeffrey Johnson [ Boise State University, Idaho, USA ]
- Scott Havens [ Snowbound Solutions, Idaho, USA ]
- Timothy Glassett [ Alaska Department of Transportation, Alaska, USA ]
- Chris Stinson [ Alaska Department of Transportation, Alaska, USA ]
- Steven Clark [ Utah Department of Transportation, Utah, USA ]
- Jerry Mock [ Boise State University, Idaho, USA ] [ Snowbound Solutions, Idaho, USA ]
- Hans Peter Marshall [ Boise State University, Idaho, USA ]
- Leighton Watson [ University of Canterbury, Christchurch, New Zealand ]
Date: 2026-09-28
Abstract: The maritime climate of Turnagain Arm, near Anchorage, Alaska, provides snow conditions conducive to the generation of frequent large avalanches, which begin as dry powdery slab releases from as high as 1200 meters above sea level and transition to a wet avalanche, or slurry, by the time they reach sea level. This study identifies and characterizes the infrasound and low-frequency acoustic signatures (below 50 Hz) associated with these rapid gravity-driven snow mass movements by examining a sequence of eight avalanches triggered by howitzer artillery during an Alaska Department of Transportation hazard mitigation campaign on January 30th, 2026. Using coincident video, we quantify these mass movements in terms of their infrasonic source intensities, signal durations, and infrasound-inferred descent velocities and use the infrasound signal morphology to characterize the dynamics of these avalanches. Specifically, we are able to differentiate wet versus dry flow signal characteristics and energetics (which are higher frequency and lower intensity for wet debris). We also use the infrasound avalanche dataset to document multiple flow pulses (within an individual avalanche) and discuss isolated discrete infrasonic pulses possibly associated with flow accelerations or decelerations.
Object ID: ISSW2026_P1.28.pdf
DOI: https://doi.org/10.15788/1790098758
Language of Article: English
Presenter(s): Jeffrey Johnson
Keywords: avalanche monitoring, infrasound, transitional avalanches
Page Number(s): 971 - 977
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