John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
If a major tsunami were to occur off the Atlantic coast, cities from New England to New Jersey could be hardest hit.
If a major tsunami were to occur off the Atlantic coast, cities from New England to New Jersey could be hardest hit by the incoming walls of speeding water.
John Ebel, an earth-sciences professor at Boston College, put his hometown and its coastal kin on the danger map during a presentation on Friday at the Seismological Society of America's annual meeting. Ebel was inspired to take up the question of East Coast tsunami damage after a "swarm" of 15 earthquakes struck about 170 miles east of Boston in April 2012, with the largest being of 4.0 magnitude. The same year, several other tremors occurred off the coasts of Newfoundland and Cape Cod along the Atlantic continental shelf.
It's clear the Atlantic can rumble. Although the ocean doesn't experience the number of tsunamis that the Pacific gets – a consequence of volcanic explosions and more shifting tectonic plates – there have been a few big ones, like the 1755 earthquake and tsunami that destroyed much of Lisbon and 1929's huge waves that crashed into Grand Banks, Newfoundland, causing surreal scenes like these:
Ebel believes that the upper East Coast is most at risk because the recent seismic activity in the Atlantic is similar to what preceded the 7.2 magnitude Grand Banks quake. That temblor triggered an underseas landslide that swamped Newfoundland with towering waves, crushing homes and killing 29 people. Ebel says:
The setting for these earthquakes, at the edge of the continental shelf, is similar to that of the 1929 M7.3 Grand Banks earthquake, which triggered a 10-meter tsunami along southern Newfoundland and left tens of thousands of residents homeless.
Ebel's preliminary findings suggest the possibility than an earthquake-triggered tsunami could affect the northeast coast of the U.S. The evidence he cites is the similarity in tectonic settings of the U.S. offshore earthquakes and the major Canadian earthquake in 1929. More research is necessary, says Ebel, to develop a more refined hazard assessment of the probability of a strong offshore earthquake along the northeastern U.S. coast.
Of course, our monitoring systems are much better today than in the 1920s, so we'd have a real-time warning of any incoming tsunamis. And many cities on the East Coast have sea walls or harbors that protect them. So it's not something to freak out about, just maybe worth a ponder – perhaps the next time you're out swimming in the ocean, alone, and notice a distant wave on the horizon.