Building codes not up for quakes

Monday, April 2, 2001 | 11:39 a.m.

Local building codes, which require homes and other buildings to be at least 5 feet from fault lines, are not enough to protect Southern Nevadans from earthquake danger, according to scientists and engineers meeting in Las Vegas last week.

Faults in Clark County are not pencil-thin lines drawn on a map, and 5 feet offers little protection to homes built near quake zones, James Werle of Converse Consultants said Friday at the end of the 36th Engineering Geology & Geotechnical Engineering Symposium at UNLV.

"Faults are not lines drawn on the ground, they are zones," Werle said, noting that one local fault, the Eglington fault, which runs from the northwest of the valley along the western edge for seven miles, is 1,000 feet wide.

There are about 100 miles of earthquake faults criss-crossing the Las Vegas Valley.

Some of the known faults may be as young as 15,000 to 35,000 years old, but no one knows how often they produce quakes of 5.0 magnitude or more, Werle said. In the 1980s experts estimated the valley had not shaken for millions of years.

Elected officials are trying to find a balance between an acceptable level of risk and affordable homes, Werner Hellmer of the Building Department said.

Werle noted developers claim it costs more to build to stricter codes, and many areas in the valley would not be available for construction.

To solve the valley's dilemma, geologist Gary Rasmussen of San Bernardino suggested inviting the U.S. Geological Survey to map the area and dig trenches on large faults so they can be dated to settle the question of how often large quakes occur.