By Amina Aslam-Mir, San Diego Supercomputer Center REHS Intern
Over the last two years, Ashley Bosa, a Boise State University (BSU) geoscience doctorate student, has worked as part of a team of scientists to investigate the mysteries of lahars — fast moving and hazardous pyroclastic currents. The team’s goal: to advance capabilities in detecting and predicting such events. Their work is made possible through the innovative use of big data garnered from an array of seismic and infrasound sensors.
“Volcanic eruptions, landslides and debris avalanches, floods from rapidly melting snow and glaciers around volcanoes, and deposits of ash and tephra mixed with a large water source are all aggravating events for lahars, which result in dangerous conditions for surrounding communities,” Bosa said. “The high speeds of movement with the tonnes of remobilized sediment cause lahars to be particularly destructive, uprooting entire buildings in some cases.”
Ashley Bosa, a Boise State University graduate student, and a fellow researcher set up mudflow monitoring equipment in the shadow of Fuego Volcano in Guatemala.
Credit: Boise State University
Over the last century, lahars have proven themselves to be a prominent volcanic threat, like in the case of the 1985 Nevado Del Ruiz eruption, whose succeeding lahar resulted in a death toll of (at least) 23,000 people. The deadly June 2018 eruption of the Volcán de Fuego in Guatemala deposited large volumes of unconsolidated ash and pyroclasts that are still being remobilized as lahars during the rainy seasons. The communities surrounding the Fuego volcano, including those in low-lying areas further away, are still impacted and threatened by these lahars every year.
“These types of events, although catastrophic at times, have catalyzed advancements in geophysical monitoring research that have produced early warning systems and forecasting ability,” Bosa said. “In the past, many projects were based on methods using mostly seismic vibration detection in order to determine how and when a lahar is occurring, however, in 2021 and 2022, our team at BSU collaborated with scientists at Michigan Technological Instituted, the Guatemalan agency National Institute of Seismology, Volcanology, Meteorology, and Hydrology (INSIVUMEH) and other local Guatemalans — on an innovative field campaign to investigate the Fuego Volcano of Guatemala.”
Most recently, their research has been published in Nature’s Scientific Reports in an article titled Infrasound Detection of Approaching Lahars.
Specifically, the scientists established an array of sensors — including infrasound arrays, broadband seismic sensors, and timelapse cameras. They also utilized drone “structure-from-motion” flights — primarily focused on two active lahar drainages on either side of Fuego. These tools used cross correlation analysis to detect flow movement and direction, as well as new infrasonic analysis and timelapse analysis to detect flow velocities and stage heights.
The Boise State and INSIVUMEH team selected Fuego Volcano as their “natural laboratory” due to the high frequency of the eruptions and seasonal rain-triggered lahars, allowing for many opportunities for observation of the events.
“Learning about these volcanic phenomena through the geophysical lens has been fascinating. I love how we can piece together several geoscience disciplines in our field research to better understand the internal flow behaviors of these volcanic hazards, which has been and remains a big challenge to those who study lahars,” Bosa said.
A total of 22 events were recorded throughout 2021 and the team’s study found that the most favorable (and dangerous) conditions for identifying lahar flows were with more forceful and upward surge fronts. They also found that sensors placed higher on the slope of the mountain were increasingly effective in detecting movement within the least amount of time. Both conclusions improved the development of methods of prediction. This included work on determining the most efficient arrangement of seismo-acoustic sensors for understanding the flow dynamics of lahars when looking at differences in wave generation between seismic and infrasound waves.
“We are moving in a very positive direction when it comes to developing better early warning systems and information dissemination to the public regarding volcanic hazards,” Bosa said. “Our team, and many others across the globe, are working on very exciting and varied approaches to researching lahars at Volcán de Fuego and other volcanoes.”
For example, in the future more advances could be made in automated systems that could rapidly analyze the amplitudes of ground vibrational tremors, which INSIVUMEH uses to determine lahar severity and destructive potential. This would decrease the time to publish notice of lahars and decrease risk to human life.
“I cannot wait to see what future research endeavors around all volcanic processes and hazards will come up with!” Bosa said.