The Land, Air, and Water Signature of Large Calving Events at Barry Glacier, Alaska
Large glacier calving events share many geophysical properties in common with landslides. Both exhibit emergent waveforms with durations of several tens of seconds. Both produce energy across a wide range of frequencies (<0.01 to >10 Hz). Both can be observed across regional seismic networks. And in areas such as coastal Alaska, landslides and glacier calving happen in the same places. Landslides are a rare occurrence, while glaciers calve all the time. These high rates of calving significantly complicate efforts to monitor landslides.
We attack this problem, in part, by characterizing the full variation in calving events at Barry Glacier, Alaska. We examine several hundred large calving events observed in seismic, infrasound, and tide gauge data. Seismic stations close to the fiord show a long period (~0.01 Hz) seismic and/or tilt response lasting tens of minutes after calving has ceased. This signal closely tracks the wave heights observed on tide gauges and reflects the oscillation of water waves (i.e., seiche) within the fiord. We assume that the amplitude of the water waves scale with the volume of subaerial ice released in calving events. By contrast, we examine the seismic energy of the actual calving process and find little relationship to the size of the water waves. Local infrasound array data produce highly reliable backazimuths that point to the glacier terminus. Like the seismic data, the infrasound energy shows no meaningful relationship to the ensuing water waves. The water waves can be observed on tide gauges at distances of 8 to 16 km. These travel at speeds of 10-20 meters per second and exhibit significant dispersion and reverberation. The water waves travel about 4% faster during periods of high tide than low tide. Together these observations help characterize the signature of large calving events on land, in the air, and in the water and demonstrate multiple ways to distinguish them from similarly sized landslides.
Session: Detecting, Locating, Characterizing and Monitoring Non-earthquake Seismoacoustic Sources
Type: Oral
Room: 209C
Date: 4/19/2023
Presentation Time: 10:45 AM (local time)
Presenting Author: Michael E. West
Student Presenter: No
Additional Authors
Michael West Presenting Author Corresponding Author mewest@alaska.edu Alaska Earthquake Center, University of Alaska Fairbanks |
Gabrielle Davy gdavy@alaska.edu University of Alaska Fairbanks |
James Gridley james.gridley@noaa.gov National Tsunami Warning Center, National Oceanic and Atmospheric Administration |
Matthew Haney mhaney@usgs.gov Alaska Volcano Observatory, U.S. Geological Survey |
Peggy Johnson peggy.johnson@noaa.gov National Tsunami Warning Center, National Oceanic and Atmospheric Administration |
Ezgi Karasozen ekarasozen@alaska.edu Alaska Earthquake Center, University of Alaska Fairbanks |
John Lyons jlyons@usgs.gov Alaska Volcano Observatory, U.S. Geological Survey |
Terry Nicols terry.nichols@noaa.gov National Tsunami Warning Center, National Oceanic and Atmospheric Administration |
Summer Ohlendorf summer.ohlendorf@noaa.gov National Tsunami Warning Center, National Oceanic and Atmospheric Administration |
Dennis Staley dstaley@usgs.gov Alaska Volcano Observatory, U.S. Geological Survey, Anchorage, Alaska, United States |
Liam Toney ldtoney@alaska.edu University of Alaska Fairbanks, Fairbanks, Alaska, United States |
The Land, Air, and Water Signature of Large Calving Events at Barry Glacier, Alaska
Category
Detecting, Locating, Characterizing and Monitoring Non-earthquake Seismoacoustic Sources
Description