Meet Alexandra (Alex) Iezzi 

Alex Iezzi is a research geophysicist at CVO. Her research focuses on using infrasound and seismic data to study and improve monitoring of volcanic events in the Cascades. Alex focuses on lahar and debris flow research and the development of detection, localization, and characterization algorithms for these types of events. Prior to working at CVO, Alex spent time researching and monitoring volcanoes in Alaska with the Alaska Volcano Observatory as both an intern with the USGS and as a graduate student at the University of Alaska Fairbanks. She is also a great communicator and can been seen in the recent video about Mount Adams Seismicity: https://www.usgs.gov/observatories/cvo/news/usgs-scientists-wes-thelen-and-alex-iezzi-talk-about-what-they-are-doing 

Fun fact, Alex also played rugby and sang a cappella in college. 
 

What is Infrasound? 

When a volcano erupts, it releases a lot of energy. Some of that energy goes into the ground in the form of seismic waves and some of that energy goes into the atmosphere in the form of acoustic, or sound, waves. Volcanoes may sound loud to those that are close to an eruption, but actually the majority of the sound from volcanoes is low frequency (below 20 Hz), which is below the threshold of human hearing. That low frequency sound is called infrasound. Infrasound sensors are microphones specifically designed to detect these sound waves in the atmosphere.

Infrasound has an important role in volcano monitoring because it can help locate and learn about volcanic eruptions, lahars, debris flows and more, especially when combined with other data such as seismic. Infrasound waves can propagate for hundreds to thousands of miles due to their low frequency but are 10 times slower than seismic waves. They travel at the speed of sound which is approximately 760 mph (340 meters per second) at sea level. 

Other things can produce infrasound like wind, ocean waves, meteors, glaciers, thunder, and aircraft. Because there are many possible sources of infrasound, more information about the direction, size, duration, and frequency of infrasound waves is needed to determine exactly what generated the signal.

Alex uses Infrasound to Monitor Volcanoes

Observing volcanoes can sometimes be difficult due to cloudy weather. Because infrasound is not affected by cloud-cover and can travel long distances, it is a useful tool to detect and monitor volcanic eruptions, especially in remote areas, like the Aleutian Islands in Alaska. 

Here in the Pacific Northwest, infrasound can be used to help monitor and detect another volcanic hazard - dangerous debris flows and lahars (volcanic mudflows). This is particularly important at volcanoes like Mount Rainier, where large lahars could travel long distances into populated valley communities. 

Using seismic and infrasound data are common tools for monitoring debris flows, but they don’t give scientists all the information they need to understand and track the flows. To help address this need, Alex and a team of scientists are working on a new and unique approach incorporating the use of a surveying tool called a laser rangefinder into debris flow monitoring. We are lucky to have Alex at CVO monitoring our volcanoes and innovating for the future!