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4.8 magnitude earthquake rattles Las Vegas valley

By: Caroline Bleakley 
Updated: May 22, 2015 06:01 PM PDT
LAS VEGAS - An earthquake about 100 miles northeast of Las Vegas shook the valley around 11:47 a.m Friday.
According to the website for the United States Geological Survey, the quake was centered near Caliente, Nevada. Initially, the U.S.G.S. reported the quake registered a magnitude of 5.4, but later downgraded it to 4.8.
There are reports of more than a dozen aftershocks ranging in magnitude from 1.0 to 3.5. Geologists said more are likely to occur.
The earthquake happened on a strike slip fault, which is a common type of fault line, north of the Las Vegas valley. Dr. Cindy Shroba from the College of Southern Nevada said it was a shallow earthquake -- an earthquake that occurs less than seven miles below the earth's surface.
"Well, it turns out that the earthquake was shallow. The shallower an earthquake is, the more energy gets dissipated on the earth's surface. And so if it were a deeper earthquake, we wouldn't feel it as much on the surface, we'd still detect it, but we wouldn't feel it," said Dr. Shroba.
Geologists say there are about a dozen identified faults that are scattered throughout the valley. They said none of them were responsible for Friday's earthquake.
Clark County Emergency Management initiated a level 1 response which means they are monitoring the situation closely.
Nevada Highway Patrol closed the off-ramps from U.S. 95 south to I-15 north and south due to damage that is earthquake related. All the ramps have since been reopened.
According to the Nevada Department of Transportation, the quake caused the rubber encasing on the bridge seam to separate causing the immediate shutdown of the US 95 southbound ramp to I-15 southbound. The separation was a six inch gap from one end to the other.
“The joint damage was pre-existing. The tremblor simply dislodged the protective rubber encasing the bridge seam making it look much worse than it was in reality,” said NDOT District I Engineer Mary Martini. “However, we're issuing an emergency contract to repair the seam. Meanwhile, the ramps remain structurally sound and safe for travel.”
The closure caused major traffic delays Friday afternoon during one of the busiest holiday traffic weekends of the year in Las Vegas.
Authorities say it is safe for drivers to use the Las Vegas roads.
"The ramp itself hasn't been compromised, therefore we're opening up," said NHP Trooper Loy Hixson. "But we do know, if there's going to be repairs done, emergency contract will be set up and we're looking at those repairs being done after the holiday weekend."
NDOT says bridges, including the ones at the spaghetti bowl, are inspected twice a year. They say they're designed to withstand strong winds and earthquakes.
About 1.8 percent of Nevada bridges are considered structurally deficient, which is lower than the national average.
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