Infrasound Signal Detection and Back Azimuth Estimation Using Ground-Coupled Airwaves on a Seismo-Acoustic Sensor Pair
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Date
2018-07-17
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Citation of Original Publication
McKee, K., Fee, D., Haney, M., Matoza, R. S.,& Lyons, J. (2018). Infrasound signaldetection and back azimuth estimationusing ground-coupled airwaves on aseismo-acoustic sensor pair.Journal ofGeophysical Research: Solid Earth,123,6826–6844. https://doi.org/10.1029/2017JB015132.
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©2018. American Geophysical Union. All Rights Reserved
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Abstract
We present a new infrasonic signal detection and back azimuth determination technique thatrequires just one microphone and one three-component seismometer. Ground-coupled airwaves (GCAs)occur when an incident atmospheric acoustic wave impinges on the ground surface and is partiallytransmitted as a seismic wave. GCAs are commonly detected hundreds of kilometers away on seismicnetworks and are observed to have retrograde particle motion. Horizontally propagating acoustic waves andGCAs have previously been observed on collocated infrasound and seismic sensor pairs as coherentwith a 90° phase difference. If the sensors are spatially separated, an additional propagation-induced phaseshift is present. The additional phase shift depends on the direction from which the acoustic wave arrives,as each back azimuth has a different apparent distance between the sensors. We use the additional phaseshift, the coherence, and the characteristic particle motion on the three-component seismometer todetermine GCA arrivals and their unique back azimuth. We test this technique with synthetic seismo-acousticdata generated by a coupled Earth-atmosphere 3-Dfinite difference code, as well as three seismo-acousticdata sets from Mount St. Helens, Mount Cleveland, and Mount Pagan volcanoes. Results from ourtechnique compare favorably with traditional infrasound array processing and provide robust GCA detectionand back azimuth determination. Assuming adequate station spacing and sampling, our technique providesa new and robust method to detect infrasonic signals and determine their back azimuth, and may be ofpractical benefit where resources are limited and large sensor networks or arrays are not feasible.