Dutch scientist finds possible cause of Europe’s deadliest earthquake; warns of repeat

Scientists have found an explanation for the deadliest earthquake in European history, which destroyed Lisbon in 1755. Earth scientist Wouter Schellart of Vrije Universiteit Amsterdam, together with colleagues from Lisbon and Mainz, has discovered a “drip structure” of dense rock deep in the ocean floor. It extends to a depth of about 200 kilometers and is slowly sinking, with implications for the seafloor and surrounding countries.

The undersea earthquake, estimated at a magnitude of 8.5 to 8.7, also triggered a tsunami at the time, causing damage across large parts of Europe. Waves were even seen in the Amsterdam canals. In Lisbon, cautious estimates put the death toll at around 50,000 people.

“The risk of a repeat event certainly exists,” said VU professor Wouter Schellart. “That structure is there and will continue to sink over the coming millions of years; that’s the only direction it can go.”

He did not venture predictions about when such a catastrophic earthquake might occur again. “That is the holy grail, but still a long way off. First, we will conduct more marine research, with seismometers on the ocean floor.”

The researchers will conduct follow-up measurements on a flat section of the ocean floor southwest of Portugal, beneath which the drip structure lies. “It had never been observed before,” Schellart explained. According to him, the location aligns with earlier rough predictions about where the earthquake occurred.

Based on a computer model, the scientists believe that the structure they observed in an upper layer caused a fault responsible for the undersea earthquake. They now plan to locate this fault.

Beneath the ocean south of Lisbon lies the boundary between two tectonic plates, the African and the Eurasian. As they move toward each other very slowly, the rock forming the drip structure is effectively being pushed downward. This process can trigger powerful earthquakes. Since smaller tremors often precede such events, measurements in the right locations could help provide warnings.

The research has been published in the scientific journal Nature Geoscience.