Palmdale Residents Unshaken by Proximity to San Andreas : Earthquakes: Experts believe that significant activity along the fault zone may wreak havoc with roads and utilities, but that houses will remain structurally sound and livable.

The huge yards in front of the houses along Palmdale’s Bayberry Street are a delight to neighborhood children. And residents can boast that they bought their homes, many of which are two-story, for only about $130,000 each last year.

Yet this is not a case of a builder gone mad. The company that developed the area was required by law to lay out the enormous yards to keep the houses back from an offshoot of the fearsome San Andreas Fault that runs under the quiet street.

The houses, some of which are 90 feet from the curb, illustrate how Palmdale--one of the fastest-growing cities in California--deals with the fearsome fault zone that crosses its southern sector.

Joseph Hrobar, 66, like other residents of Bayberry Street, says he isn’t concerned about what might come, even after watching the carnage wrought by last month’s 7.1-magnitude temblor in the Bay Area. “When will the Big One come? Maybe tomorrow, maybe 100 years. If we are worried about it all the time, what is life?”

Scientists say it is only a matter of time before a “great” earthquake (one with a magnitude of at least 8) rips through Southern California. The forecasters predict a 60% chance within 30 years for that quake to originate somewhere in the region. There is a 30% chance for such a quake to spring from the Mojave section of the San Andreas that runs through the Antelope Valley.

A great quake could be especially bad news for Palmdale. Because the fault runs through the city, it is expected to get a severe shaking from any great quake along the San Andreas in Southern California. Within Los Angeles County, Palmdale--with a population of 46,000--is one of the most developed areas crossed by the fault.

“It’s going to be a real ‘E’ ride, and we’ve got ringside seats to the main event,” said Mark Spykerman, a Lancaster engineering geologist who advises Antelope Valley developers on their projects.

Estimates differ, but geologists predict that a great earthquake will cause a 10- to 20-foot shift of land from one side of the main fault to the other, enough to slide the slow lane of the Antelope Valley Freeway into the fast lane. If that doesn’t close the freeway, forecasters say landslides or road collapses are likely between Palmdale and the San Fernando Valley.

The result, earthquake experts say, is that Palmdale probably would be cut off from the Los Angeles area for at least several days. If such a temblor should strike during a workday, many thousands of Palmdale residents who work in the Los Angeles Basin would be blocked from returning home.

Within the city, damage would be extensive. One picture of how a quake might affect Palmdale came from a 1982 state report envisioning a repeat of the 8.3-magnitude Fort Tejon quake of 1857, the last time the portion of the San Andreas through the Antelope Valley broke loose.

In and around Palmdale, major regional arteries might be severed, including two major Southern Pacific railroad lines and the California Aqueduct that serves Los Angeles, the state report said.

The aqueduct, the major channel moving water north to south, crosses the San Andreas at two points near Palmdale. The aqueduct could be closed for three to six months while workers try to repair expected ruptures, the state report said. Leaks from the aqueduct or Palmdale Lake, a reservoir for the city, could hamper general repair efforts.

The runways at Air Force Plant 42 in Palmdale, where the city of Los Angeles hopes to build a regional airport, are predicted to survive the quake, which would allow relief supplies to be flown in. But the state report forecasts that a major regional natural gas transmission line running through the city could be ruptured and have to be closed.

Not all would be lost, though, even in a great quake. The good news for Palmdale is that experts believe that most of the many thousands of homes built since the tougher seismic standards of the 1970s, including those on Bayberry Street, would come through battered but structurally sound and livable.

In fact, because most of the city has sprung up in recent years, most buildings are earthquake resistant, experts say. The city has only a few buildings even five to six stories tall. And, unlike Los Angeles, Palmdale has no older unreinforced masonry buildings, the most vulnerable in earthquakes.

Many in Palmdale minimize the impact that a great quake might have. After the Bay Area quake, the city’s building and safety director and its earthquake coordinator suggested that Palmdale would actually suffer less shaking in a major quake because of its proximity to the fault. But several earthquake experts flatly dismissed the idea.

George Housner, a professor of engineering at Caltech, said that should the great quake emanate from the San Andreas in Southern California, communities within five miles of the fault would clearly receive a more severe shaking than Los Angeles. The fault is more than 40 miles from the Los Angeles city limits.

In Palmdale, home developments are common in the San Andreas fault zone, a swath about a mile wide that includes the main fault and several lesser ones. Homes can be built within the zone but cannot be directly atop a fissure.

A state law enacted in the early 1970s established special studies zones that extend an eighth of a mile on either side of the outer limits of faults. The law requires that homes built within the zones be set back from fault traces. The law recommends 50 feet, but the distances can be more or less. And in some cases, houses must have special foundations.

Bayberry Street is in such a zone and--like other residents interviewed--Michael Tong isn’t worried.

“This is California,” said Tong, a machinist who works in Pasadena. “You can go everywhere and there are earthquake faults.”

Tong, his wife and two children moved to Palmdale about a year ago from a small house in the Los Angeles area. For about $125,000, they got a brand-new, much larger home in a better neighborhood.

If he moved now, Tong said, it would mainly be for a shorter drive to work rather than to flee the San Andreas.

* WAITING FOR THE QUAKE

Special report appears in Section Q.