Hurricanes Can Trigger 'Stormquakes' in the Ocean Floor in New Geophysical Phenomenon

Strong storms, such as hurricanes, can generate vibrations in the ocean floor known as stormquakes which are equivalent in strength to minor earthquakes, a team of researches has found. The team, led by Wenyuan Fuan—an assistant professor of Earth, Ocean and Atmospheric Science at Florida State University—has described this newly identified geophysical phenomenon in a study published in the journal Geophysical Research Letters. According to the researchers, the phenomenon is the result of powerful storms transferring some of the vast amounts of energy that they produce into the Earth's crust—the thin, rocky outer layer of our planet.

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"We're calling them 'stormquakes,'" Fuan said in a statement. "During a storm season, hurricanes or nor'easters transfer energy into the ocean as strong ocean waves, and the waves interact with the solid earth producing intense seismic source activity." For their research, the scientists examined seismic activity data stretching from September 2006 to February 2019 which had been collected from around the coasts of the North American continent. Analysis of these figures using a newly developed method revealed that more than 10,000 vibrations, or stormquakes, had occurred in the ocean floor near the edge of continental shelves (portions of continents which are submerged under shallow sea) and ocean banks (parts of the seabed which are shallow compared to surrounding areas) off the shores of New England, Florida, and the Gulf of Mexico in the United States, as well as the waters of Nova Scotia, Newfoundland and British Columbia in Canada.

For example, they found that Hurricane Ike in 2008 produced several storm quakes in the Gulf of Mexico, while the same occurred with Hurricane Bill in 2009—a storm that generated stormquakes in the waters off New England and Nova Scotia. "We initially designed a method to locate earthquakes," Fuan told Newsweek. "Accidentally, we detected some earthquake-like signals, but they seemed to have clear seasonalities." "The seasonalities suggest the detected seismic sources might be more likely from the ocean or the atmosphere because earthquake occurrence does not have a clear seasonality," he said. "We then comparatively studied the ocean wave models, and found the strong correlation between stormquakes and strong storms." The stormquakes that the team documented measured as much as 3.5 on the Richter magnitude scale which would make them about the same strength as minor earthquakes. The scientists also found that these stormquakes can last for a relatively long time. "We can have seismic sources in the ocean just like earthquakes within the crust," Fan said. "The exciting part is seismic sources caused by hurricanes can last from hours to days." It is still not clear exactly why some storms produce stormquakes and some do not. For example, the powerful Category 3 Hurricane Sandy did not produce any stormquakes. Furthermore, the phenomenon only seems to occur in certain areas, with the researchers not detecting any in the waters off Mexico, for example. The researchers say that this issue needs to be investigated further to understand the factors at play, although it is likely that local features on the seafloor are important. "We have lots of unknowns," Fan said. "We weren't even aware of the existence of the natural phenomenon. It really highlights the richness of the seismic wave field and suggests we are reaching a new level of understanding of seismic waves." The scientists also suggest that stormquakes are a common but overlooked natural phenomenon in Western Europe and Western Australia, as well as North America.