Infrasound Array Observations of the Recent Explosive Eruptions of Mt. Redoubt, Alaska

Infrasound signals produced by the recent explosive eruptions of Mt. Redoubt, Alaska, demonstrate the potential for acoustic remote sensing of eruptions. From March 23 to April 5, 2009 (UT), Mt. Redoubt, located 166 km SW of Anchorage, Alaska, was volcanically active resulting in approximately 30 explosive events as recorded by seismometers in Alaska. During that time, it produced ash plumes that reached as high as 19.8 km above sea level† and ejected a significant amount of ash. Not only did the airborne ash cause numerous flight delays and cancellations, but enough ash accumulated in Anchorage to prompt the closure of the Ted Stevens Anchorage International Airport. Many of these explosive episodes were powerful enough to generate infrasound signals that were detected by numerous stations, some located more than 4000 km away. A single infrasound microphone located 12 km from Mt. Redoubt’s vent recorded peak-to-peak pressures of 100 Pa or greater for approximately half of the explosive episodes, the loudest of which was estimated to be approximately 343 Pa. The I53US infrasound array located in Fairbanks, Alaska (546 km from Redoubt) detected approximately 25 events consistent with a 31 minute propagation delay and recorded peak-to-peak pressures of 10 Pa or greater for 4 events. Infrasound signals consistent with event times and acoustic propagation speeds were also clearly detected at Newport, Washington (I56US, 2627 km from Redoubt), Dundas, Greenland (I18DK, 3385 km from Redoubt), and Kona, Hawaii (I59US, 4553 km from Redoubt). The strong explosions at Redoubt - with known origin times and source strengths - are useful for source and propagation studies. Results from the analysis of data from the aforementioned arrays and others within a range of 6000 km will be presented. † http://www.avo.alaska.edu/activity/Redoubt.php