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Using Remote Hydroacoustic Recordings to Track Volcanic Unrest Near the Taʻū Islands, American Samoa

A seismic swarm near Taʻū Island, a volcanic island in eastern American Samoa, occurred from July to October 2022. The earliest unrest was noted as felt reports in late July, and instrumentation varied in the beginning of the sequence as the Hawaiian Volcano Observatory responded by installing temporary and then permanent seismometers to monitor the activity. The network variability made it difficult to characterize the earliest seismicity and contextualize the entire sequence to discriminate between an underlying tectonic or volcanic source. Here we present results analyzing hydroacoustic detections from International Monitoring System hydrophone arrays near Wake Island, 4500 km northwest of Taʻū volcano. Using least-squares beamforming analysis, we create a catalog of T-wave detections from the direction of Taʻū volcano to track the earthquake rate. Both the rate and hydroacoustic pressures, which we interpret as a proxy for earthquake magnitude, gradually increased from late July to August, peaking on August 19 (rate) and August 24 (magnitude), before gradually decreasing to background in late September. Minutes-long bursts of tremor were also contemporaneously recorded from the moment the permanent broadband seismometers were installed on August 20. Tremor activity continued throughout the rest of August, peaking on August 25, before ending in early September. These tremor bursts were band-limited to ~1-5 Hz and were recorded as S-waves at a distal station on Tutuila Island, 230 km to the west of Taʻū Island. Our preliminary results do not constrain the earthquake or tremor locations (which may not be co-located), but we interpret the increase in earthquake size and rate, together with the occurrence and characteristics of the tremors, to be the result of magmatic activity beneath Taʻū, volcano.

Session: Seismoacoustic, Geodetic and Other Geophysical Investigations of Active Volcanoes [Poster Session]

Type: Poster

Room: Exhibit Hall

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Aaron Wech

Student Presenter: No

Additional Authors