Associated Press
Scientists at the University of Nevada, Reno, are scrutinizing seismic readings and studying damage at residents' homes to try to figure out what's happening beneath Earth's surface under a northwest Reno neighborhood rocked by a seemingly endless string of earthquakes.
What they can't say is whether the hundreds of temblors that have rattled the area for two months—the largest a magnitude 4.7 Friday night—are subsiding or a prelude to bigger things to come.
"You're not going to get an earthquake prediction today," John Anderson, director of Seismology Laboratory at the University of Nevada, Reno, said Tuesday during a briefing with Governor Jim Gibbons and emergency managers on the seismic activity.
Scientists are calling the swarm of temblors that began February 28 the "Mogul earthquake sequence," in reference to the neighborhood where hundreds of mostly minor earthquakes have occurred.
But the shaking is unusual, seismologists say, because the intensity of the quakes has increased over the past few weeks. Generally, earthquakes tend to occur and are followed by smaller aftershocks.
In this case, the earth's rumblings have continued unabated, with barely negligible bumps occurring often minutes apart, followed by occasional larger shakers.
It's impossible to know if the temblors are foreshocks of a bigger quake to come or aftershocks of what has been, experts said.
Day After the Day After Tomorrow?
Up until April 15, sizable quakes that could be felt were occurring about once every third day.
Then the rate increased, with about three, 2.0 or larger incidents occurring daily.
On April 24, when the first 4.2 quake was registered, "all of a sudden we were seeing 20 [of the magnitude] 2s and larger per day," said state geologist Jon Price.
Earthquake magnitudes are calculated according to ground motion recorded on seismographs. An increase in one full number—from 5.5 to 6.5, for example—means the quake's magnitude is 10 times as great.
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