ABSTRACT

Collaborative Research: Quantifying explosive volcanism in Alaska using seismo-acoustic wavefields recorded by USArray

Alaska is home to 130 potentially active volcanoes, of which more than 50 have been active in historical times. On average 2 volcanoes are in a state of eruption every year. Volcanoes in the Aleutian Islands, Alaska Peninsula, and Cook Inlet are capable of sudden, explosive, ash-cloud forming eruptions, which are potentially hazardous to passenger and freight aircraft along this heavily travelled air corridor. Many of Alaska?s volcanoes are in remote locations with harsh environments. Monitoring these volcanoes represents a formidable challenge and many of the volcanoes are not instrumented. Infrasound (acoustic waves with frequencies below the 20 Hz hearing threshold of the human ear) is a rapidly developing technology to understand and monitor explosive volcanic eruptions. Modest-sized explosive eruptions produce powerful infrasound signals that propagate efficiently over thousands of kilometers in the atmosphere. However, to date, these signals have been recorded by sparse infrasound sensor networks, limiting our understanding of their source generation and propagation through the atmosphere. The EarthScope Transportable Array (TA) is currently being deployed in Alaska, bringing the densest ever combined seismic and infrasonic network to one of the world?s most active volcanic regions. Exploiting this novel dataset, this project will advance the capability of acoustic early warning systems of volcanic eruptions for aviation safety and will assess the potential contribution of large sensor networks such as the TA to volcano monitoring. At the end of the project, an operational volcano-acoustic monitoring system resulting from this work will be implemented at the Alaska Volcano Observatory.

This work will capitalize on the unprecedented seismo-acoustic dataset starting to become available as the TA records Alaska?s routine explosive volcanism with dense spatial wavefield sampling. Volcano seismo-acoustics is a rapidly advancing research field, where basic questions remain on the source mechanisms, source directionality, atmospheric propagation, and seismo-acoustic coupling from explosive volcanic eruptions. This project will focus on detection, discrimination, and location of the signals using novel methods; quantifying the seismo-acoustic wavefield; investigating the source mechanisms; quantifying seismo-acoustic wave coupling; and understanding infrasound propagation in the spatio-temporally varying atmosphere. Through a combination of data analysis and modeling, we will characterize and quantify diverse seismic and infrasonic signals recorded at a range of distances and directions from the explosive eruption source. We will address the following questions: (1) How do observed acoustic and seismic signals from explosive volcanic eruptions vary with distance and azimuth to the source? (2) How does acoustic propagation differ for various types of explosive eruptions? (3) What kind of volcanic source information can be determined from long-range seismo-acoustic data? (4) What are the wavefield sampling limitations in previous volcano infrasound studies? (5) What other infrasound sources are present in Alaska? Our team will work with the EarthScope National Office at the University of Alaska Fairbanks to help highlight this research and its impacts. Multi-media products illustrating seismo-acoustic wavefields from volcanic eruptions in Alaska will be distributed via the web for use in public information packets and education and outreach. Event catalogs and related data products will be publically available, with notable infrasound events uploaded to the IRIS TA Infrasound Reference Event Database (TAIRED).

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