A mysterious, globally observed and unprecedented 9-day-long seismic signal in September 2023 was caused by a massive landslide in Greenland.
A mysterious, globally observed and unprecedented 9-day-long seismic signal in September 2023 was caused by a massive landslide in Greenland. 25 million m3 of rock and ice fell into the remote Dickson Fjord and, in turn, caused a 200 metre-high mega-tsunami that continued sloshing back and forth - a phenomenon called a seiche - in the narrow fjord for 9 days. That is the conclusion of research published in the journal Science. This movement of a large mass of water generated vibrations through the Earth, shaking the planet and radiating globally observed seismic waves. Never before have scientists observed such an unusual mechanism causing a global seismic signal.
A mysterious seismic signal lasting 9 days was discovered by puzzled seismologists on highly sensitive sensors all over the globe, from the Arctic to Antarctica, in September 2023. The signal looked completely different to frequency-rich earthquake recordings - it contained only a single vibration frequency, like a monotonous-sounding hum. At the same time, news of a large tsunami in a remote North East Greenland fjord reached authorities and researchers working in the area. The two teams joined forces in a multidisciplinary group involving a unique collaboration of 68 scientists from 40 institutions in 15 countries, combining seismometer and infrasound data, unique field measurements, on-the-ground and satellite imagery, and simulations of tsunami waves. The team also used imagery captured by the Danish military who sailed into the fjord just days after the event to capture the collapsed mountain-face and glacier front along with the dramatic scars left by the tsunami. It was this unique harmony of local field data and remote, global-scale observations that allowed the team to solve the puzzle and reconstruct the extraordinary cascading sequence of events in September 2023. The results are now published in Science.
Read more at University of Oxford
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