In September 2023, a massive tsunami in remote eastern Greenland triggered seismic waves that captured the attention of researchers worldwide.

The event created a week-long oscillating wave in Dickson Fjord, according to a new report in The Seismic Record.

Angela Carrillo-Ponce of GFZ German Research Centre for Geoscience and her colleagues identified two distinct signals in the seismic data from the event: one high-energy signal caused by the massive rockslide that generated the tsunami, and one very long-period (VLP) signal that lasted over a week.

Their analysis of the VLP signal—which was detected as far as 5000 kilometers (3100 miles) away—suggests that the landslide and resulting tsunami created a seiche, or a standing wave that oscillates in a body of water. In this case, the seiche was churning for days between the shores of Dickson Fjord.