UNLV team to conduct seismic experiments

Jennifer Knight

Monday, July 28, 2003 | 11:11 a.m.

Cathy Snelson wants to make an impact on her community -- by detonating more than 7,500 pounds of explosives throughout the valley next week.

Snelson, a geologist with the University of Nevada, Las Vegas, and her crew expect to set off charges at 10 spots throughout Las Vegas from Aug. 9 through Aug. 12 to create seismic waves underground.

The large-scale experiment represents an attempt to find out more about how earthquake fault lines work and where they are located.

"Pretty much nothing has ever been undertaken like this in the valley before," Snelson said. "We are trying to really get a detailed view of the basin itself."

Construction crews will begin drilling holes this week in preparation for the experiment. Explosives will be placed in holes 150 feet underground and set off late at night to avoid people who may be wandering around the sites.

Some 825 seismic instruments buried in the ground at various locations will record the activity.

"Some residents will be aware of the explosions because there are a few sites that are near homes and buildings," said Joe Dodd, operations manager for Sanders Construction in Henderson, the company that will help set up the experiment.

Dodd and Snelson said no foundations of buildings will be damaged by the explosions, though, and area residents are not likely to bothered by the explosions because the holes will be plugged with clay and gravel to muffle the sound.

Setting up for the experiment took months because UNLV was required to notify residents within about 1,000 feet around the blast sites, Dodd said. The exact radius for notification varied according to city ordinances for Las Vegas, Henderson, North Las Vegas and Clark County.

The university also got permission from the Bureau of Land Management and private property owners to do the experiments. After that, the construction company obtained approvals from area fire departments to conduct the blasts, Dodd said. The construction company is carrying a $5 million insurance policy on the experiment just in case anything goes wrong.

So far, eight fault lines have been detected throughout the Las Vegas basin, but not much is known about where they are or how they might shake during a major earthquake. What is known, Snelson said, is that Las Vegas is built like a bowl of jelly. The fault lines are deeper in the center and then trail off at the edges.

"We know we may never see one in our lifetime, but we do have the potential for a 6.5 or 7 magnitude earthquake here," Snelson said.

To put that in perspective, the 1994 earthquake in Northridge, Calif., was a magnitude 6.7 quake and caused 57 deaths, 1,500 injuries and property loss totaling $15 billion, according to California Institute of Technology seismology reports.

Snelson said building codes are not as stringent in Las Vegas and an quake of that strength here would cause tens of thousand of casualties.

Developing so-called shake maps and historical information is crucial to being able to understand where the fault lines are and predict their behavior.

"That's the problem we have," Snelson said. "We don't have any historic research of when the last major event happened. So there's no telling when the next earthquake will be."

The information gathered from next week's experiment, which is assisted by a $150,000 grant, will be fed to geologists at the University of Nevada, Reno, the state's hub for seismological information.

"We're really trying to work with UNLV because we're trying to build a statewide network," said UNR seismologist Ken Smith, who is helping with the project.

Snelson and Smith are not only collaborating on mapping the valley but also building a statewide seismology network that places motion sensors in the ground at area grade schools to detect any movement.

Snelson said next week's experiment is a good start to getting first responders prepared and informing residents of any potential earthquakes.

"If everything works well and all of my blasts go off, we should have some good data -- hopefully," she said.