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Soundquakes: Seismo-Infrasonic and Seismo-Infra-Seismic Phases During a Swarm of Earthquakes at Kilauea Volcano on September 30th, 2021

Seismic waves produced by earthquakes can shake the ground and produce infrasound either local to an infrasound station (i.e., primary infrasound) or from locations away from the recording site, which then propagate sound sub-horizontally toward the station (secondary infrasound). This study focuses on infrasonic waves generated by ~20 earthquakes occurring during a one-hour period prior to a summit eruption of Kilauea starting at 01:21 UTC on September 30^th, 2021. These small earthquakes (M<=2.7) were shallow (<2 km) and all but two were located near the Halema'uma'u crater. A network of three infrasound arrays located about 3 km E, ENE, and ESE of Halema'uma'u crater was operational during this swarm and recorded prominent (infrasonic) air phases from these earthquakes.

The infrasound arrays were capable of detecting infrasound and also determining apparent velocities, which ranged from those expected for horizontal sound to faster velocities associated with primary infrasound. Backazimuth projection of the infrasound showed that secondary sources from a single ‘soundquake’ typically lasting tens of seconds originated from a range of directions apparently from different topography around the Kilauea Caldera excited by ground motion. Several locations, including the western caldera walls of Kilauea, appear to be particularly pronounced ‘hotspots’ for infrasound generation. The networked array of sensors is useful for triangulating many of these sources using reverse time migration and beam information.

The unique topology of the Kilauea infrasound network of arrays permits particularly high resolution mapping of earthquake infrasound radiators. A significant finding is the prevalence of earthquake infrasound and its (perhaps) poorly appreciated impact upon the seismic wavefield. Similarly-shaped signal envelopes for the coda wave decay for both infrasound and seismic energy suggests that some of the infrasound is re-transmitted to the ground. This energy, contributing to the seismic coda, represents the prevalence of an underappreciated seismo-infrasonic-seismic phase in the seismic records.

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: Jeffrey Johnson

Student Presenter: No

Additional Authors