Residents of Emery County may still feel rather rattled. But geologists with the Utah Geological and Mineral Survey are rubbing their hands with glee at the rare opportunity to study the effects of three moderately sized earthquakes that rolled through Sunday afternoon.
No serious injuries or damage were reported.State and federal geologists headed to Emery County Monday for field work on the effects of the quakes, the largest of which registered 5.6 on the Richter scale - the region's largest earthquake since a 1975 quake near Pocatello, Idaho.
"People shouldn't be spooked out of their minds by this," said state geologist Genevieve Atwood. People in Emery County should take time to learn about earthquakes so they can "look forward to the next one without a lot of anxiety."
Sunday's quakes were centered about 14 miles east of Ferron in the San Rafael Swell area. The first quake was recorded at 12:59 p.m. and registered a magnitude 3.5 on the Richter scale. It was followed at 1:08 p.m. by a stronger jolt measuring 4.3 magnitude and a third with a 5.6 magnitude at 2:03 p.m., said the U.S. Geological Survey's National Earthquake Information Center in Golden, Colo. The quakes were also registered by the seismograph center at the University of Utah.
None of the three earthquakes broke the earth's surface (a quake must usually register 6.0 to break the surface). Atwood said several minor shocks between the second and third quakes were recorded, though most passed unnoticed by Utah residents.
Atwood said residents in the area may be subjected to some aftershocks, but it's doubtful they will be very powerful. "They released an awful lot of energy," she said.
Geologists are particularly excited about the Emery County earthquakes because they occurred along "hidden faults" previously unknown to geologists. And they were strong enough to be felt as far away as Colorado and New Mexico, as well as in northern Utah.
For years, geologists have studied the "bowl of Jell-O" syndrome of earthquakes - the idea that valleys take the brunt of the earthquake shaking, while the bedrock in the surrounding mountains act as a bowl to reflect the quakes.
"The Emery quakes will give us a more sophisticated look at that idea," Atwood said.
Sunday's earthquakes were particularly felt in Utah's valleys, while they went less noticed in the mountain areas, Atwood said. "This quake may tell us how solid the bowl of Jell-O is in our valleys," Atwood said.
There were quite a lot of reports from Utah Valley and Park Meadows (Summit County) that may support the theory that valleys shake more than mountains.
Atwood admits Utah geologists don't know a whole lot about earthquakes along "hidden faults" in Eastern Utah. But they do know a lot about faults along the Wasatch Front.
"If you look at the historical earthquakes in Utah of 4.0 or greater, most of them go right down the center of the state with a few stray ones (six) in the eastern part of the state," she said. "Those occurred on faults we didn't recognize."
Officials from the state Division of Water Rights and the federal Bureau of Reclamation were dispatched to the region Monday to check the structural safety of various reservoirs.
Geologists William Case was also in Emery County Monday studying rock falls. "We got a lot of ground shaking with this quake," said Atwood, "and that resulted in a lot of rock fall. We want to get a sense of which rocks fell and how far they rolled. We also want to take a look at which rocks didn't dislodge and why."
Rock falls in some areas blocked roads Sunday but caused no damage to roads or property.
The Emery County earthquakes should teach Utahns a valuable lesson, said Atwood. Just because you don't live along the Wasatch Front doesn't mean you won't be subjected to strong earth tremors.
Still, state geologists will continue to focus the lion's share of their attention of the Wasatch Front faults where "a whopper" of an earthquake is expected in the next 50 to 100 years. "It's enough to scare us to death," Atwood said.