Quake watch

Thursday, Feb. 24, 2000 | 10:59 a.m.

Many residents move to Las Vegas from California thinking they've left the danger of earthquakes behind. After all, scientists say there hasn't been an earthquake in the Las Vegas Valley for at least 100,000 years, while they are common in California.

But as they mark Earthquake Awareness Week this week, scientists note that a temblor rocking Southern Nevada is not a remote possibility.

New research shows, scientists say, that Frenchman Mountain on the eastern side of the valley could have been jolted within the past 10,000 to 20,000 years, but they don't have the evidence to tell when it could become active again.

In addition, preliminary evidence in both the southeast and northern ends of the Las Vegas Valley shows that earthquakes have occurred much closer to modern time than previously suspected.

Earthquake experts meeting in Las Vegas last week said Southern Nevadans need to prepare to minimize damage and prevent injuries from a magnitude 6 or larger temblor -- one similar to the quake that rocked nearby Death Valley last year and could occur closer to home.

Scientists have not mapped the Las Vegas Valley for potential earthquake activity because they believed the possibility was remote.

The state's efforts to learn about earth movements have been concentrated in northern and western Nevada, where most large earthquakes have erupted in the past 150 years.

Nevada is third in earthquake activity behind California and Alaska.

Seismology professor emeritus Burt Slemmons urged experts statewide to fill information gaps in Southern Nevada caused by rapid growth. As houses are built, geologic evidence of earth movement is paved and built over, he noted.

Southern Nevada may not be in danger of erupting like Southern California, Slemmons said, but officials do need more information about local faults. It would be hard to thoroughly map the valley after so much development, he said.

Maps are not being drawn, but Southern Nevada is taking greater note of seismic activity. More earthquake monitors are being installed around the Las Vegas Valley, and they are being tied into the seismographs at the University of Nevada, Reno's network to record temblors.

But it's not just local faults that pose a danger. Earthquake activity near Southern Nevada could shake the Las Vegas Valley as well, Slemmons said.

After the 7.1 magnitude Hector Mine quake in the Southern California desert on Oct. 17, which was felt in Las Vegas, Slemmons toured the area. He noted that two major earthquakes -- the 1992 Landers 7.5 magnitude quake and the Hector Mine temblor -- occurred in the same area, but the more recent Hector Mine rupture was 20 miles closer to Las Vegas.

"The activity probably won't continue east into Las Vegas, but it could produce strong ground motion in Las Vegas," Slemmons said, urging the council to fund future studies of earthquake activity in Southern Nevada. Such funding generally comes from Congress.

If an earthquake were to hit Southern Nevada, fallen buildings would not be the only danger. Nevada could experience high waves called tsunamis, as well.

Craig dePolo of the Nevada Bureau of Mines and Geology in Reno said scientists have estimated a tsunami 30 feet high could occur at Lake Tahoe or Lake Mead. The Mead Slope fault could produce such a wave with a temblor of 6.0 magnitude, dePolo said.

The Big One -- one measuring over 6.0 magnitude -- rattling either Reno or Las Vegas could happen once in 500 years, causing an estimated $60 million in damage, dePolo said.

The good news is that if an earthquake ever rocked Southern Nevada, Las Vegas should survive quite well, he said.

The valley has few old buildings, said Ronald Lynn, assistant director of Clark County's Building Department.

"After all, we blow them up," he said, alluding to several recent resort implosions.

That's a distinct advantage in an earthquake. All resorts built since the late 1970s exceed Uniform Building Code requirements, he said.

By making people aware of earthquake dangers, the experts hope to prevent deaths, Lynn said.

If the ground starts moving, occupants should duck under a heavy table or desk or stand under an inside door frame of a home or office, the experts say. Many people are injured by falling objects or flying glass when they run outside during a quake.

Many homeowners in Southern California have started to bolt their homes to the foundation and tie down water heaters and heavy objects such as book shelves.

Nevada experts urge local residents to do the same, since prevention is the key.

The best advice for homeowners from quake experts is preparation. A safety kit containing enough water and food for three days, battery-operated flashlights, extra blankets, clothing and first-aid supplies can be used in any emergency.