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April 19th - anniversary of Shishaldin 1999 and Pavlof 1986!

Ground-coupled airwaves and explosion signals at Shishaldin

5th anniversary of the Redoubt 2009 eruption

Loss of Critical Volcano Monitoring Information in Alaska


Loss of Critical Volcano Monitoring Information in Alaska

Report released: Geochemical investigations of the hydrothermal system on Akutan Island, July 2012

24th Anniversary of the 1989-90 eruption of Redoubt Volcano

Veterans Day slideshow

Call for images from active and retired service members!

AVO operations during lapse of federal government appropriations

New Tool for Reporting Alaska Volcanic Ash Fall Allows Residents to Assist Scientific Monitoring

25 years monitoring Alaska volcanoes - press release

AVO slideshow for Veterans Day

Large ash eruptions: when volcanoes reshape valleys -- free public lecture

Father Hubbard and the history of exploration in the Valley of Ten Thousand Smokes - free lecture

Remote sensing and volcanoes - free public lecture

The Great Eruption of 1912 - free public lecture

Archaeology of Katmai area and the impact of past eruptions - free public lecture

Historical Photography of the Great 1912 Eruption - free public lecture

Catastrophic Eruptions and People -- free public lecture

Eruption of an Island Volcano: Kasatochi, 2008 -- free public lecture

Exploring the Plumbing System of Katmai Volcanoes

Exploration of Katmai and the Valley of Ten Thousand Smokes - free public lecture

Commemorative presentation in Kodiak: Be Prepared!

Earthquakes Below Alaskan Volcanoes - free public lecture

DisaStory - A Day of Oral History

1912 Katmai Eruption Children's Program

Monitoring Alaska's Volcanoes - free public lecture

Landmark volcano study: Katmai Centennial Perspectives free download

Special activities on AVO's website for 1912 centennial

Alaska Park Science - Volcanoes of Katmai and the Alaska Peninsula

AVO at the Alaska Aviation Trade Show and Conference May 5-6

The Great Katmai Eruption of 1912 - a free lecture in Anchorage: April 24, 2012

The Great Katmai Eruption of 1912: A Century of Research Tracks Progress in Volcano Science

April 25 -- The Novarupta - Katmai 1912 eruption: a free lecture in Fairbanks by Judy Fierstein

Summer lecture series on Alaskan volcanism

Poster contest celebrates anniversary of Katmai eruption!

Mark your calendar: April 24 public lecture on the great Novarupta-Katmai eruption of 1912

An important volcanic anniversary in Alaska!

PUBLISHED: The 2009 Eruption of Redoubt Volcano, Alaska

2011 Alaska Interagency Operating Plan for Volcanic Ash Episodes now available

How does Cleveland's lava dome compare to Redoubt's 2009 lava dome?

Alaska Volcanoes Guidebook for Teachers

New Fact Sheet on Kasatochi

How big is the 2009 Redoubt lava dome?

New map: Historically active volcanoes of Alaska

Steaming at Augustine

Sarychev Volcano: Active Volcanoes of the Kurile Islands

Footage of Alaska's Redoubt Volcano taken on Monday, March 23, 2009.

Pre-eruption footage of Redoubt Volcano, Saturday, March 20, 2009

Redoubt Volcano B-Roll Footage

Kasatochi 2008 eruption summary

6th Biennial Workshop on Subduction Processes emphasizing the Kurile-Kamchatka-Aleutian Arcs Geophysical Institute, University of Alaska, Fairbanks, Alaska

Chiginagak volcano's acid crater-lake continues to supply acidic, metal-laden water to salmon spawning habitat on the Alaska Peninsula


20 years of AVO

Viewing earthquake information for Alaska volcanoes

Pavlof webcam added

Activity at Pavlof volcano

Pavlof thermal anomaly

AVO Scientists present at U.S. Department of Education Teacher-to-Teacher Workshop

Cleveland webcam available

Activity at Cleveland volcano

Cleveland satellite images

Sheveluch Eruption

U.S. Geological Survey's alert notification system for volcanic activity

KVERT Volcanic Warnings Ceased

New alert system for volcanic activity

Three new webcams added

AGU presentations requested

New webcam available

Infrasound Detection of Volcanic Explosions
Infrasound Detection of Volcanic Explosions
Posted: July 26, 2012
Monitoring volcanic eruptions in Alaska is often challenging due to the remoteness of many of the volcanoes in the region, making a local monitoring network difficult to establish and maintain. Cloudy weather also regularly hinders the ability of satellites to detect eruptions. Recent studies have demonstrated how infrasound, or low frequency sound waves, can be used to detect, locate, characterize, and quantify volcanic eruptions.

When a volcano erupts, it releases energy into the ground in the form of seismic waves and into the atmosphere in the form of acoustic (sound) waves. The majority of the sound from volcanoes is low frequency (below 20 Hz, the lower threshold of human hearing) and is termed infrasound. Nearly all types of volcanic eruptions produce infrasound, and infrasound from large, explosive eruptions can travel up to thousands of miles due to the low amount of energy loss in the atmosphere. This is in contrast to seismic waves in the Earth, which encounter considerably more energy loss. The Alaska Volcano Observatory (AVO), in conjunction with the Geophysical Institute (GI) of the University of Alaska Fairbanks, has a number of infrasound stations deployed in Alaska. Sensitive microphones at these stations record infrasound. Seismometers also occasionally detect infrasound waves, as the sound energy may shake the ground near the seismometer creating a “ground-coupled airwave”. Scientists at AVO and the GI analyze the infrasound and ground-coupled airwave data to determine if a volcano has erupted.

Infrasound waves travel at the speed of sound, approximately 340 m/s (760 mph) at sea level, thus taking about 15 minutes to travel every 300 km (185 miles). Their propagation is determined by the temperature and wind structure ofin the atmosphere, and therefore a detailed knowledge of the atmosphere and the prevailing winds is necessary to understand the long-range propagation of sound. In addition, strong winds on the ground can create high noise conditions and potentially obscure the infrasonic signal.

Because infrasound is not affected by cloud-cover and can travel long distances, it is a useful tool to monitor volcanic eruptions in Alaska. For example, the recent eruptions of Redoubt Volcano in 2009 and Kasatochi and Okmok Volcanoes in 2008 all produced significant infrasound detected in Alaska and up to 4000 miles away. The ongoing eruption of Cleveland Volcano has also been detected by infrasound microphones and seismometers in Alaska and the Aleutian Islands. In fact, distant infrasound recordings and ground-coupled airwaves are often the only data used to detect explosions from Cleveland Volcano due to its remoteness, lack of a local seismic network, and consistently poor weather.

--David Fee
URL: www.avo.alaska.edu/news.php
Page modified: January 28, 2014 18:55
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