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In a captivating new study, scientists have cracked the mystery behind a global seismic signal that puzzled experts last September. The study, published in The Seismic Record, reveals how a Greenland megatsunami triggered seismic waves that lasted nine days.

Tsunami Triggers Global Seismic Signals

In September 2023, a massive tsunami in eastern Greenland caused seismic waves felt worldwide. Researchers were intrigued by the event, which involved a rockslide-triggered tsunami in Dickson Fjord. This catastrophe produced two distinct seismic signals: one high-energy signal from the rockslide and a long-lasting Very Long Period (VLP) signal from a seiche in the fjord.

Angela Carrillo-Ponce and her team from GFZ German Research Centre for Geoscience detected these signals. The VLP signal, observed up to 5,000 kilometres away, indicated a persistent seiche—a standing wave—churning in the fjord for over a week.

Carrillo-Ponce remarked, “The global reach of the seiche signal is remarkable. It highlights how a remote Greenland event can be tracked worldwide.” She added that studying this event seismically revealed new insights into fjord dynamics and seiche behaviour.

Implications for Climate Change and Future Monitoring

The research underscores the growing importance of monitoring Greenland's landslides and climate impacts. Recent tsunamis in Greenland, like the 2017 Karrat Fjord disaster, have already demonstrated the risks posed by unstable slopes and melting glaciers.

The team used seismic data and satellite imagery to pinpoint the landslide’s impact. They found the tsunami's run-up exceeded 200 metres near the fjord's entry point. The detailed analysis also confirmed that the VLP signal's long duration matched the seiche model, offering valuable data for future studies.

Carrillo-Ponce's team believes this approach can enhance our understanding of similar past events and their links to climate change. “The data shows how seismic signals reflect the type of source and energy radiation,” she concluded.