Mount Rainier lahar detection system receives major upgrade

Mount Rainier lahar detection system receives major upgrade
by Clarence Oxford
Los Angeles CA (SPX) May 03, 2024

Approximately 90,000 individuals reside within the potential lahar path of Washington State's Mount Rainier, a zone vulnerable to fast-moving volcanic debris flows known as lahars.

During the 2024 Annual Meeting of the Seismological Society of America (SSA), Seth Moran, a volcano seismologist with the U.S. Geological Survey, presented recent enhancements to a lahar detection system designed to alert communities near the Seattle-area volcano.

Lahars, primarily triggered by volcanic eruptions through the rapid melting of snow and ice, can also originate under non-eruptive conditions. These include scenarios where volcanic structures weaken over time due to past eruptions and spontaneously collapse, generating landslides that evolve into lahars.

Historically, large lahars have traveled from Mount Rainier to the Puget Lowlands, a distance of about 50 kilometers, on at least 11 occasions over the last 6000 years. These lahars can reach speeds up to 100 miles per hour on steep slopes and 15 to 20 miles per hour across flatter terrains.

"All of the lahars that have come down into the Puget Lowlands in the last 6000 years have started with an eruption except for the most recent one around 1507," Moran stated. This recent event, the Electron Mudflow, began with a landslide, and no evidence suggests it was associated with an eruption.

Originally established in 1998, the Mount Rainier Lahar Detection System provided downstream communities with vital minutes of warning. The initial system, constrained by the technology of the 1990s, had limitations such as low bandwidth and power requirements, leading to data transmission delays.

Since 2016, the system has been upgraded with advanced instruments, including broadband seismometers for continuous real-time data, infrasound sensors, and webcams. Researchers are also exploring the use of laser range finders as a potential replacement for tripwires.

Moran highlighted the challenges of relying on a single type of instrument for lahar detection, given the rarity of such events globally. The diverse instrumentation aids scientists in distinguishing lahar-induced seismic signals from those caused by eruptions or earthquakes.

The updated system now enables immediate data transmission to two emergency operations centers operated by the state of Washington and Pierce County, which are staffed around the clock. Upon detecting a lahar, these centers assess the threat and initiate appropriate warning procedures