An increase in seismic activity in the North Atlantic suggests that New England is most at risk of suffering the effects of a tsunami in the near future, according to a Boston College seismologist.
Over the past year there have been 12 small earthquakes at the edge of the continental shelf – about 170 miles east of Boston – with the most powerful being a magnitude 4 quake that occurred April 12, 2012, says John Ebel, of Boston College's Weston Observatory, which studies earthquakes.
"I can't put a number on the chances of it happening, there's no way of knowing timing," he says. "But when we have more frequent small earthquake activity, there's a greater chance of having a larger one in the future."
Ebel presented preliminary findings of his research Friday at the Seismological Society of America's annual meeting in Salt Lake City.
Tsunamis are extremely rare, but not unprecedented in the Atlantic Ocean. Ebel says tectonic conditions in the Pacific and Indian Oceans make tsunamis more likely in those regions; recent tsunamis in Japan and Indonesia killed thousands. In 1929, a magnitude 7.2 earthquake off the coast of Newfoundland caused a tsunami to hit Canada, killing 27 people, destroying thousands of homes and cutting transatlantic communication lines.
"I'm drawing an analogy from the 1929 area to this area that reaches to Boston," Ebel says. "Geologically, it looks the same. The earthquakes are occurring right at the edge of the continental shelf."
His research, based on several decades of earthquake data, suggests that the coasts between Nova Scotia and New Jersey are at highest risk for a tsunami.
"As you go further south than New Jersey, there are no reports of earthquakes at all at the edge of the continental shelf," he says.
Ebel says in order for a tsunami to cause major damage, there needs to be an earthquake of a magnitude of at least 7, which are rare on the East Coast. The earthquake also has to occur in the ocean; some seismologists believe the earthquake has to be powerful enough to cause what is known as a "submarine landslide," which pushes sediment off the continental shelf and into the deep ocean.
The most powerful earthquake to strike the East Coast in recent memory was a magnitude 5.8 quake that struck near Richmond, Va., in 2011. The earthquake that caused at least 220,000 deaths in Haiti in 2010 was a magnitude 7.0 quake that struck land. Ebel says that quake was not associated with a tsunami.