Scientists still learning from Alleghany County earthquake nearly two years later

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Geologists who’ve been studying the earthquake that damaged hundreds structures in the northwest corner of the state nearly two years ago say it was stranger than anyone first realized.

Paula Figueiredo, a postdoctoral research assistant at NC State University, is lead author of a new study on the earthquake site.

Using images from drones and radar, scientists found something never previously documented on the East Coast — an earthquake-caused rupture at the surface. It was more than a mile long.

“No one was expecting that a magnitude five earthquake will actually break the ground surface. Generally, those earthquakes do not make all the way to the surface. So we don’t actually see the direct effects of surface faulting when those earthquakes happen,” Figueiredo said.

The rupture, which marks a previously unknown fault line, buckled roads and created stepped inches averaging a few high along its length.

At a magnitude of 5.1, the Aug. 9, 2020, quake was the strongest in the state for more than a century, and in Alleghany County, at least 100 homes were believed damaged — many with cracked foundations. The quake was felt in nearby states including Virginia, South Carolina, and Tennessee.

In 1916, a magnitude 5.5 quake occurred near Skyland, the National Weather Service said.

Days later, specialists from the University of Memphis traveled to North Carolina to monitor aftershocks.

The University of Memphis’ Center for Earthquake Research and Information, with help from North Carolina US geological survey officials and four portable seismograph stations in a tightly controlled pattern to record the aftershock.

At least 12 aftershocks have been recorded near Sparta in Alleghany County. A magnitude 2.9 aftershock rattled the town two days after the quake while Gov. Roy Cooper was touring the town.

Also, eight small foreshocks were identified, the university said.

WUNC’s Celeste Gracia contributed to this report.

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