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Mighty storms have been discovered that trigger earthquake-like seismic activity

  Stormquake Illustration

A Florida State University researcher has discovered a new geophysical phenomenon in which a hurricane or other strong storm can trigger seismic events in the nearby ocean that are as strong as an earthquake of magnitude 3.5.

] "We call them & # 39; stormquakes & # 39 ;," said lead author Wenyuan Fan, an assistant professor of earth, ocean, and atmospheric science. "This involves the coupling of atmosphere, ocean and solid earth. During a storm season, hurricanes or norhers transmit energy as strong ocean waves into the ocean, and the waves interact with the solid earth and produce intense seismic source activity.

The study was published in the journal Geophysical Research Letters. [1

9659003] Fan and his colleagues analyzed nearly a decade of seismic and oceanographic records from September 2006 to February 2019 and found a connection between strong storms and intense seismic activity on the edge of continental shelves or seabanks.

  Wenyuan Fan FSU

] Assistant Professor Wenyuan Fan coined the term "stormquake" to describe a newly identified geological phenomenon in which hurricanes or other strong storms trigger seismic events. Image credits: Bruce Palmer / FSU Photography Services

In particular, researchers found evidence of more than 10,000 storms from 2006 to 2019 off the coast of New England, Florida and the Gulf of Mexico in the US and off the coast of Nova Scotia. Newfoundland and British Columbia in Canada.

"We can have seismic sources in the ocean, just like earthquakes in the crust," Fan said. "The exciting part is seismic sources that are caused by hurricanes and can last for hours to days."

Fan and his colleagues developed a novel approach to detect and locate seismic events and determine if the seismic event is a stormquake. It must occur on a stormy day and meet other geophysical standards to determine the robustness of the correlation between the storm and the seismic event. In addition, other seismic events such as earthquakes must be excluded.

An example the researchers cited was Hurricane Bill, an Atlantic hurricane that originated on August 15, 2009, which became a Category 4 hurricane and eventually hit Newfoundland as a tropical storm. It was a category 1 hurricane approaching the coast of New England on August 22, 2009.

When the hurricane arrived, numerous seismic events were located off the coasts of New England and Nova Scotia, producing transcontinental surface waves.

Similarly, Hurricane Ike caused a stormquake in the Gulf of Mexico in 2008, and Hurricane Irene in 2011 did the same near the Little Bahama Bank off Florida's coast.

Fan and his colleagues found that this was not all hurricanes causing stormquakes. There are hotspots. Scientists found no evidence of stormquakes off Mexico or from New Jersey to Georgia in the United States. Even Hurricane Sandy, one of the most expensive storms in the US, has not triggered a stormquake.

This suggests that stormquakes are strongly influenced by local oceanographic features and seabed topography, Fan said.

"We have many of unknowns," Fan said. "We were not even aware of the existence of the natural phenomenon This really underscores the richness of the seismic wave field and suggests that we are gaining a new understanding of the seismic waves. "

Researchers from the Woods Hole Oceanographic Institution and the Scripps Institution of Oceanography and the US Geological Survey contributed to this research

Reference: "Stormquakes" by Wenyuan Fan, Jeffrey J. McGuire, Catherine D. de Groot-Hedlin, Michael AH Hedlin, Sloan Coats, and Julia W. Fiedler, October 14, 2019, Geophysical Research Letters .

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