Earthquake scientists stressed Thursday that the Wells, Nev., quake was not related to the Wasatch Fault that runs through highly populated areas of Utah and that it was extremely unlikely to trigger any movement of that fault.

"There's nothing that I understand to suggest anything will be happening on the Wasatch Fault," said Kristine Pankow, assistant director of the University of Utah Seismograph Stations.

The system of faults involved in the Nevada event was the Independence Valley Fault Zone, not Utah's Wasatch Fault. But Pankow said it should serve as a wake-up call because "we're in earthquake country, and these events — though infrequent — happen here." And experts agree that the Wasatch Fault is due for a stronger earthquake.

U. earth scientists drove toward the epicenter of the Wells quake on Thursday, taking portable seismic detectors to record detailed information about the depth, direction, intensity and ground movement of aftershocks.

By 10 a.m. MST, less than three hours after the first strong shaking, there were around 20 aftershocks of magnitude 3.0 and larger recorded by the stations' equipment in Utah, Pankow said.

Throughout Thursday the National Earthquake Information Center in Denver listed several aftershocks smaller than 3.0, although at 4:57 p.m. Utah time, a sizable aftershock was recorded at 4.6 magnitude. Aftershocks were occurring "primarily west of the main shock," according to Susanne Janecke, associate professor of geology at Utah State University.

The center listed the Nevada main earthquake as magnitude 6.0, located 12 miles east of Wells and 151 miles west of Salt Lake City. The break occurred about 5.6 miles beneath the surface at 6:16 a.m. local time (7:16 a.m. in Utah). Residents reported they felt it as far away as Salt Lake City, Ogden, Logan and Delta in Utah, and in more distant locations in Idaho.

Pankow said scientists "want to know where the aftershocks are occurring with a higher precision, and with the current distribution of stations we can't do that." Together with specialists from the University of Nevada at Reno and the U.S. Geological Survey, the Utahns were setting up specialized instruments near the epicenter.

The U. planned to deploy five to 10 monitors, she said. Small aftershocks could continue for weeks or months, according to Pankow.

The Wells event is considered a moderate earthquake. "But we have to keep in mind that damage relates more to the built environment," she said. "So if you have a lot of older buildings or weak construction, a magnitude 6 can do some significant damage."