DOI: 10.25349/d9903g
title: 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

description: 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 &lt;105 m3 and durations &lt;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.
description: 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
description: A README.txt file contains the methodology described above. No
 data is available between the individual video files provided.