Scientists see greater quake danger: More studies on LV faults find new dangers

Friday, March 30, 2001 | 10:46 a.m.

New evidence shows the Las Vegas Valley is prone to larger and more frequent earthquakes than previously believed, scientists attending a conference at UNLV were told today.

Southern Nevada's faults have not been studied enough, putting Las Vegas residents at a greater risk if they remain unprepared, according to experts presenting new research at the annual Engineering Geology and Geotechnical Engineering Symposium at UNLV.

After running a computer model, geology consultants John Perry and Jim O'Donnell, both of Boulder City, concluded that a quake in the Las Vegas Valley larger than 6.0 magnitude could be devastating.

"We found that there would be over 10,000 casualties and $11 billion in total economic losses," their study concludes.

Up to 386 deaths could occur and more than 3,300 people would be hospitalized if a big one hit Las Vegas. The scientists ran their computation on faults both west and east sides of the valley.

That damage assessment is much worse than a study released last year by the Federal Emergency Management Agency.

In the September report, FEMA ranked Nevada fifth in the nation for estimated losses from an earthquake and pegged statewide damages at $55 million, $28 million of the total in Las Vegas.

Nevada is the third most earthquake prone state in the nation, behind California and Alaska.

Although Northern Nevada has a greater quake danger, Perry and O'Donnell concluded, Las Vegas has a much higher damage potential because of the size of its population.

Seismologists first paid attention to earth movements in Las Vegas in the 1960s, when nuclear weapons were exploded underground at the Nevada Test Site, said O'Donnell, who tracked ground motion for the government and now consults with UNLV scientists. After the United States stopped underground nuclear weapons tests in 1992, experts such as O'Donnell turned their attention to natural faults in the Las Vegas Valley.

"It should aid our local governments and communities in assessing the demands of a major earthquake -- for example, shelter and hospital requirements," they said of their latest estimate.

Small earthquakes triggered in the valley during the 1990s may be a wakeup call that Southern Nevada is far more active than experts and planners once thought, said an expert from the University of Nevada, Reno Mackay School of Mines.

Earthquake faults that extend north and south along Decatur Boulevard and one that cuts through Sunrise Mountain east of the valley may be part of larger networks with the potential for bigger earthquakes, said Burt Slemmons, emeritus professor at the University of Nevada, Reno.

Slemmons lives in Las Vegas and felt firsthand a Feb. 3 quake with a 3.5 magnitude that rocked the valley on a previously unknown zone called the West Charleston fault.

Faults that lie deep underneath the valley and are not visible at the surface pose the greatest risk.

Bulldozers and buildings have covered much of the Las Vegas Valley's faults, erasing evidence of earlier earthquakes on the valley's surface.