April 22, 2024

A new detection method aims to warn of tsunamis caused by increasingly frequent landslides!

A debris field from the October 2015 landslide extends over the crest of Tyndall Glacier and into Tan Gorge in the spring of 2016. Photo: Chris Larson
Christian Garavaglia Christian Garavaglia Argentina meteorite 6 minutes

Researcher in Fairbanks University In Alaska you have one A method developed to detect large landslides within minutes of their occurrence To see from a distance and quickly determine if they are close to open water and a Tsunami danger Represent.

In a new paper, researchers claim that their method of determining the location, extent and impact of a landslide is fast enough to meet the National Oceanic and Atmospheric Administration's (NOAA) goal of detecting a tsunami within five minutes to issue a warning.

“Glaciers are retreating due to global warming “It leaves behind valleys whose slopes have lost their support,” explains seismologist Ezge Karasuzun of the UAF Geophysical Institute. “This is important, especially in areas like the south coast of Alaska, because Large land masses can flow into the water and cause tsunamis“.

There is a big difference between an earthquake and a landslide

Karasozin's article, co-authored by Michael West, a seismologist and director of the Geophysical Institute's Alaska Earthquake Center, warns of the danger by pointing out Landslide in 2015 This released more than 75 million cubic meters of rock into Alaska's Tan Strait off Icy Bay, 105 kilometers northwest of Yakutat.

According to the site phys.org he A prototype system from Karasözen and West has been able to detect in real time in the Barry Arm area of ​​Prince William Sound since August In process. It uses data from seismic stations located in the Alaska network.

Glaciers, landslides and tsunamis
Holgate Glacier in Kenai Fjords National Park, Seward, Alaska, United States.

State and federal authorities fear a landslide and tsunami could occur in Barry Arm, where the Pari Glacier has retreated, leaving an unreinforced wall of the fjord that has collapsed about 200 meters in recent decades. Subsequent analysis of Barry Arm seismic station data revealed three landslides that occurred in 2020 and 2021.

The instability “raises concern that a catastrophic rupture could trigger a tsunami with a maximum wave height of several metres, which could impact surrounding communities in just 20 minutes,” Karasuzen and West said.

“When an earthquake occurs, there are devices that measure the height of sea waves, and tsunami warning centers are put on alert after the earthquake,” Karasuzen said. “But landslides are not systematically monitored in Alaska or anywhere else in the world. If there was a tsunami caused by a landslide, we wouldn't know about it. That's very concerning.”

the US Geological Survey Leads interagency and multidisciplinary monitoring in this area.

How does the new landslide detection method work?

The method of Karasözen and the West is Long-period landslide waves soon emerge amid a seismic record full of short-period waves To identify those caused not only by landslides but also by earthquakes, glaciers and human activities in the area.

The onset of a landslide is usually recorded as short-term waves; Only when the landslide accelerates do noticeable long-period waves appear. Landslides produce a disproportionately larger amount of long-lasting energy than other sources. Most seismic explosions last only seconds, while landslides usually last a minute or more.

Karasuzen and West's approach is to quickly identify the long-period waves of a landslide amid a seismic record full of short-period waves.

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Coastal fjords pose a major challenge for landslide detection Glaciers can produce hundreds of stunning seismic events every daywrite the researchers.

Karasuzin and West developed an algorithm that continuously analyzes seismic data from different seismic stations looking for a landslide wave signal. If a match is found, the system calculates the location and size of the landslide. In areas with good seismic station coverage, the location can be estimated with an accuracy of a few kilometers.

Need for real-time alarm

The system aims to alert tsunami and earthquake authorities personnelbut there is still a lot to do.

Many researchers have shown that seismograms of landslides can be used to estimate their location and magnitude, but such attempts are usually limited to a specific area, require significant modifications, and are not implemented. Not designed for real time purposes.

Determining landslide locations from remote seismic stations Real-time evaluation is not allowedThis is because seismic waves take a long time to reach these stations.

West says the research complements ongoing monitoring and warning efforts. “The ability to monitor large landslides in real time is an important part of Alaska's ongoing multi-agency landslide response effort.”He said.

Source note:

Ezge Karasuzen et al., Toward rapid seismic assessment of landslides in coastal Alaska, Seismic Record (2024). doi: 10.1785/0320230044