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Supporting information for: A pilot experiment on infrasonic lahar detection at Mount Adams, Cascades: Ambient infrasound and wind-noise characterization at a quiescent stratovolcano: time-lapse camera images

Citation

Sanderson, Richard; Matoza, Robin; Haymon, Rachel; Steidl, Jamison (2021), Supporting information for: A pilot experiment on infrasonic lahar detection at Mount Adams, Cascades: Ambient infrasound and wind-noise characterization at a quiescent stratovolcano: time-lapse camera images, Dryad, Dataset, https://doi.org/10.25349/D9903G

Abstract

Erosion, hydrothermal activity, and magmatism at volcanoes can cause large and unexpected mass wasting events. Large fluidized debris flows have occurred within the past 6,000 years at Mount Adams, WA, and present a hazard to communities downstream. In August 2017, we began a pilot experiment to investigate the potential of infrasound arrays for detecting and tracking debris flows at Mount Adams. We deployed a telemetered 4-element infrasound array (BEAR, 85-m aperture) ~11 km from a geologically unstable area where mass wasting has repeatedly originated. We present a preliminary analysis of BEAR data, representing a survey of the ambient infrasound and noise environment at this quiescent stratovolcano. Array processing reveals near-continuous and persistent infrasound signals arriving from the direction of Mount Adams, which we hypothesize are fluvial sounds from the steep drainages on the southwest flank. We interpret observed fluctuations in the detectability of these signals as resulting from a combination of (1) wind-noise variations at the array, (2) changes in local infrasound propagation conditions associated with atmospheric boundary layer variability, and (3) changing water flow speeds and volumes in the channels due to freezing/thawing and precipitation events. Suspected mass movement events during the study period are small (volumes <105 m3 and durations <2 minutes), with one of five visually confirmed events detected infrasonically at BEAR. We locate this small event, which satellite imagery suggests was an ice/snow avalanche, using three additional temporary arrays operating for five days in August 2018. Events large enough to threaten downstream communities would likely produce stronger infrasonic signals detectable at BEAR. In complement to recent literature demonstrating the potential for infrasonic detection of volcano mass movements (Allstadt et al., 2018), this study highlights the practical and computational challenges involved in identifying signals of interest in the expected noisy background environment of volcanic topography and drainages.

Methods

Individual images in the time-lapse videos are from a PlotWatcher Pro camera at the BEAR site. This camera looks west, and sees all the solar panels and the equipment vault. Weather conditions and snow depth are also captured. Six photos are taken each day: at 10 AM, 11 AM, 12 PM, 1 PM, 2 PM, and 3 PM (Pacific Daylight Time, PDT). Image overlays show the station name, local date and time (PDT, 24-hour clock), battery level %, temperature (°F), and moon phase. This camera comes with software (Game Finder 1.4) that links all the photos for each day into a TLV-format video clip. The TLV files are converted to AVI-format, and then merged into continuous video records using FFmpeg (free open-source software). MP4-format files are also provided which contain the same data.

Time periods covered uninterrupted (YYYY-MM-DD format, PDT):

2017-09-01 to 2018-06-30

2018-07-07 to 2018-08-29

2018-10-12 to 2019-06-19

2019-07-02 to 2019-10-05

2019-10-05 to 2020-07-19

2020-07-19 to 2020-10-21

Usage Notes

A README.txt file contains the methodology described above. No data is available between the individual video files provided.

Funding

National Science Foundation, Award: EAR–1614855

National Science Foundation, Award: EAR–1847736