Exeter College Fellow helps solve mystery of unidentified nine-day-long seismic event
Professor Paula Koelemeijer, Tutorial Fellow in Earth Sciences at Exeter College, was part of an extensive team who investigated an unprecedented nine-day-long seismic signal that occurred in Greenland last year, initially leaving scientists baffled as to the signal’s source.
In September 2023, Dickson Fjord, Greenland was the site of a massive landslide, which in turn created a mega tsunami reaching 200 metres high (about twice the height of the Statue of Liberty), which sloshed back and forth in the narrow fjord. This phenomenon produced a seismic signal that repeated every 90 seconds for nine days. The landslide was caused by the collapse of a mountaintop, stemming from glacial thinning over recent decades caused by rising average temperatures. The volume of material that collapsed was more than 25 million cubic metres. The cause of the signal was originally a mystery, being very different from earthquake signals that normally are frequency rich and would typically only last a few hours to days, depending on the strength of the earthquake. This signal, however, contained only a single vibration frequency.
As a seismologist and Fellow at Exeter College, Professor Koelemeijer’s research focuses on long period standing waves of the Earth that occur after large earthquakes and allow us to answer fundamental questions about Earth’s interior. This led her to be part of the group formed of 68 scientists from 40 institutions in 15 countries who studied the seismic phenomenon. Together the team combined seismometer and infrasound data, as well as newly acquired imagery from the Danish military. This combination of data allowed the team to triangulate the source of the signal and reconstruct the sequence of events.
With rapidly accelerating climate change causing glacial thinning, landslide-generated tsunamis such as this one are expected more regularly. Professor Koelemeijer recently explained to the BBC’s Science In Action programme: “It is therefore crucial to install more instruments to be able to understand the deatiled landslide dynamics and detect the events quicker so that if they happen, we might have some warning, especially if there are cruise ships sailing around these fjord systems.”
You can read the full results in Science and listen to Professor Koelemeijer’s interview on BBC Sounds.
