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Earthquake swarm rattles Reno

RENO, Nev. -- A series of more than 30 earthquakes that rattled the Reno area over the past two days occurred on the most significant fault structure in the area, and scientists are monitoring for potentially bigger shock waves to follow, experts said Wednesday.

The quakes began Tuesday evening and continued into Wednesday morning. The largest -- a magnitude-4.4 late Tuesday -- shook homes and businesses in a 300-square-mile area near the Nevada-California line.

No significant damage was reported.

Graham Kent, director of the Nevada Seismological Lab at the University of Nevada, Reno, was at home when the biggest quake hit and described it as "quite a jolt."

"I was basically right on top of it," he said. "In scientific terms, it was a 4.4. But for us, it was one heck of a kick in south Reno."

Kent told CBS affiliate KTVN the quakes were "a big wake up call to take these seriously."

"Pretty much all large quakes start with small quakes. That's not always the case, but we tend to have these swarms and every once in a while it throws out a 6.5 or something," Kent said.

Scientists are paying close attention because it happened near a fault structure that has the potential for the largest earthquakes in the Truckee Meadows, along the Sierra Nevada's eastern front.

"We are monitoring it as we speak to see if it slows down or kicks back up," Kent said.

The largest temblor's epicenter was about seven miles south of downtown Reno, the lab reported. It was felt as far as 50 miles east, near Silver Springs; 80 miles northeast in Quincy, California; and 100 miles southwest in Grass Valley, California.

Two magnitude-3.1 quakes bookended that quake.

"No, it's not the wind," the National Weather Service in Reno tweeted at about 11 p.m. Tuesday. "There have been 3 earthquakes this evening all centered on the south side of Reno."

"Pretty much all large quakes start with small quakes. That's not always the case, but we tend to have these swarms and every once in a while it throws out a 6.5 or something," Kent said..

Crews were on scene Wednesday at Galena High School about 3.5 miles from the epicenter but found no obvious damage, Washoe County school officials said. Police had no reports of significant problems, and the Truckee Meadows Water Authority said there was no sign of any harm caused to water mains.

"It was right on the borderline of where you'd be expecting to see some damage -- just underneath the level where you start cracking a lot of plasterwork and things start moving," Kent said.

The fault structure links five individual fault lines that begin at Lake Tahoe, about 40 miles southwest of Reno.

"In 2005 we had just shy of a magnitude-5," Kent said. Since then, the same fault structure produced a magnitude-4.2 in Spanish Springs in 2013, and one as large as 4.9 in Mogul in 2008 that caused an estimated $1 million in damage.

"People ask me if there is going to be another one," Kent said. "In our own decadal history here, Spanish Springs didn't have another one, but Mogul had a larger one after the initial force. So we're basically batting .500 right now. After this, we will either be batting .333 or .667."

Laced with faults, Nevada is the third most seismically active state, behind California and Alaska. A magnitude-6.0 temblor near the northeast Nevada town of Wells in 2008 was the biggest in the state in four decades, causing nearly $10 million in damage.

"Learn to secure your space," Kent advised. "If you're looking at that beautiful picture above your bed it's time to move it out and not put it back up there. Last night was a time to make you think."

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