May 2016 – GEOLOGY – A new study found pieces of the mantle under this region have been periodically breaking off and sinking down into the Earth. This thins and weakens the remaining plate, making it more prone to slipping that causes earthquakes. The study authors conclude this process is ongoing and likely to produce more earthquakes in the future. ‘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 in the Journal of Geophysical Research – Solid Earth, a journal of the American Geophysical Union. ‘Based on distinct variations in the geometry and thickness of the lithospheric mantle and foundered lithosphere, we propose that piecemeal delamination has occurred beneath the region throughout the Cenozoic, removing a significant amount of reworked/deformed mantle lithosphere,’ the team wrote.
Compared to earthquakes near plate boundaries, earthquakes in the middle of plates are not well understood and the hazards they pose are difficult to quantify. The new findings could help scientists better understand the dangers these earthquakes present. 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.