Earthquakes along the East Coast are rather rare. However, a new study has shown that the North American Plate is peeling off. What this means is that pieces of the mantle under this region have been periodically breaking off and sinking into the Earth. Causing the plate to weaken, and make the plate more prone to slipping.
Our idea supports the view that this seismicity will continue due to unbalanced stresses in the plate,” said Berk Biryol, a seismologist at the University of North Carolina at Chapel Hill and lead author of the new study. “The [seismic] zones that are active will continue to be active for some time.” The study was published today in the Journal of Geophysical Research — Solid Earth, a journal of the American Geophysical Union.
Earthquakes in the middle of the plate are not well understood, and they pose an “unknown” hazard.
“Today, the southeastern U.S. is more than 1,056 miles from the nearest edge of the North American Plate, which covers all of North America, Greenland and parts of the Atlantic and Arctic oceans. But the region was built over the past billion years by periods of accretion, when new material is added to a plate, and rifting, when plates split apart. Biryol and colleagues suspected ancient fault lines or pieces of old plates extending deep in the mantle following episodes of accretion and rifting could be responsible for earthquakes in the area.
“This region has not been active for a long time,” Biryol said. “We were intrigued by what was going on and how we can link these activities to structures in deeper parts of the Earth.”
Further proving the point of what another geologist mentioned recently about the New Madrid Fault getting ready to crack within the next few years.
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To find out what was going on along the East Coast, they “cat” scanned it:
“the researchers created 3D images of the mantle portion of the North American Plate. Just as doctors image internal organs by tracing the paths of x-rays through human bodies, seismologists image the interior of the Earth by tracing the paths of seismic waves created by earthquakes as they move through the ground. These waves travel faster through colder, stiffer, denser rocks and slower through warmer, more elastic rocks. Rocks cool and harden as they age, so the faster seismic waves travel, the older the rocks.”
Over the next few years, earthquakes along the Eastern Coast are due to rise exponentially because the underside peeling will allow the plate to slide more. Since the inevitable New Madrid fault is due for another quake over the next few years as well, it is entirely plausible that there will be an exponential rise in earthquakes all around the East Coast and Midwest.
University of North Carolina at Chapel Hill. “Likely cause for recent southeast US earthquakes: Underside of the North American Plate peeling off.” Science Daily. . (2016): . . https://www.sciencedaily.com/releases/2016/05/160503130840.htm