On August 23, 2011, a magnitude 5.8 earthquake shook the Piedmont region in Virginia. Four days later, Hurricane Irene struck the U.S.’s East Coast. As it passed by, the rate of aftershocks in Virginia increased “sharply,” Nature.com notes.
Just a coincidence?
Zhigang Peng, a scientist from Atlanta’s Georgia Institute of Technology, reports that there was indeed an “unusual pattern” to the aftershocks after the Virginia earthquake.
As Peng explained at a recent meeting of the Seismological Society of America in Salt Lake City, Utah, what usually happens after an earthquake is that the rate of aftershocks decreases with time, but a study of seismic records for the Virginia earthquake reveals that the aftershocks increased as Hurricane Irene passed by, with some 700 aftershocks occurring. The change was not initially noted because the aftershocks were small, with a magnitude of less than 2.0 and other, less sensitive devices did not detect them.
Peng and his research team hypothesized that, as the hurricane made its way up the East Coast and atmospheric pressure dropped, it affected the forces on the fault that had caused the Virginia earthquake. On more examination of the aftershocks, Peng ended up finding that these had increased the most when the storm was moving away, rather than when the barometric pressure was at its lowest.
While a drop in the atmospheric pressure does not seem to be what triggered the aftershocks, Peng remains “confident that there was a change in the aftershock rate during the storm’s passage.”
Other Research On Hurricanes and Extreme Weather As Triggers to Earthquakes
Peng’s and his team’s findings are correlations and not actual proof of a hurricane-earthquake link. Another seismologist, Martin Chapman, of Virginia Polytechnic Institute and State University in Blacksburg, points out that other factors including tidal forces at the moon could be at play.
Nature.com cites other research that links hurricanes and earthquakes: American and Taiwanese researchers have found a correlation between slow earthquakes, which can take over hours or days, and tropical cyclones in Taiwan.
In addition, Shimon Wdowinski, a seismologist at the University of Miami in Florida, thinks that hurricanes — specifically “extremely wet tropical cyclones striking Taiwan” — are associated with “big earthquakes that occur up to three years later.” The cyclones, Wdowinski contends in yet-to-be-published research, lead to the erosion of landslide debris, which “triggers a change in fault loading, eventually producing an earthquake.”
At a meeting of the American Geophysical Union in the months after both the Virginia earthquake and Hurricane Irene, researchers described the weight of heavy rain from monsoons in the Himalaya Mountains in Nepal actually “bends the whole underground system of tectonic plates.” While this added pressure is at first in opposition to that on the tectonic plates, after the water washes away in the winter, the plates “rebound” and the “release of pressure adds a tiny amount of stress that may be enough to trigger impending earthquakes.”
Scientists plan to study the pattern of aftershocks that Peng has noted. If a connection between extreme weather events and hurricanes can be found, it could be a helpful predictor of when impending earthquakes might happen. Such could aid us in building structures that would help us to build safe, or safer, structures in a climate changed world, even while we continue efforts to try to combat global warming and its causes.
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