Scientists Discover Tremors Caused By Hurricanes

Washington – Scientists discovered a mixture of two feared disasters – hurricanes and earthquakes – that can last for days and feel like an earthquake of magnitude 3.5.

The shaking of the sea floor during hurricanes and other strong storms can feel like a thunderous earthquake and can last for days, according to a study in this week's issue of the Geophysical Research Letters. Earthquakes are common, but were not noticed before because they were considered background noise.

The phenomenon is more strange than dangerous, because nobody is at the bottom of the sea when a hurricane occurs, said Wenyuan Fan, a seismologist at the University of Florida who was the main author of the study.

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"It's the last th ing you should worry about," Fan told The Associated Press.

Storms unleash huge waves in the sea, which causes another type of wave. Those secondary waves then interact with the sea floor – but only in certain parts – and that causes the shocks, Fan said. It only happens in places where there is a large continental shelf and shallow flat land.

Fan's team detected 14,077 of those earthquake-storms between September 2006 and February 2015 in the Gulf of Mexico and in front of Florida, New England, Nova Scotia, Terra Nova, Labrador and British Columbia. A special sensor for military use is necessary to detect them, Fan said.

Hurricane Ike in 2008 and Hurricane Irene in 2011 unleashed numerous such phenomena, says the study.

The jolt creates a wave that seismologists do not look for when monitoring earthquakes, which explains why they have not been noticed so far, says Fan.

The seismic waves generated by the ocean are recorded in the instruments of the United States Geological Survey, "but in our mission to search for earthquakes those waves were considered background noise," said seismologist Paul Earle.

The study makes sense and is interesting, because it examines a frequency of waves that scientists have not studied much, said geophysics professor Lucia Gualteri of Stanford University.

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