L.A. Subject to Same Jolt but Is Better Built

On any given day in metropolitan Los Angeles, there are half a dozen faults capable of creating an earthquake like the explosive magnitude 7.4 temblor that struck Turkey before dawn Tuesday, killing thousands. But a similar quake here would have far less devastating results, earthquake experts said Wednesday.

The reason is less a matter of seismology, fault planes or geodesy than of bricks and mortar.

When it comes to earthquake engineering, California has perhaps the world’s strictest building codes, which have been updated regularly over the decades as experience with urban earthquakes has grown. More important, those codes have been more strictly enforced, several experts said. Retrofitting in recent years has been extensive.

That means there are fewer old buildings with unreinforced masonry or unbolted foundations, which readily collapse in even mild earthquake shaking.

In Southern California, more people also live in flexible, wood-frame homes, not the concrete high-rise apartments common in urban Turkey. The quality of housing construction--also a major cause of casualties in a severe 1995 quake in Kobe, Japan--may have been the key factor in the high death toll from the most recent urban earthquake disaster.

“We are better prepared because we are better off economically and have more funds to put into each building,” said UCLA geophysicist David Jackson. “We have lived through Northridge and Loma Prieta and survived, but we could still have nasty surprises.”

Indeed, the economic consequences of a similar major earthquake in the heart of Los Angeles or the San Francisco Bay Area would be catastrophic. A magnitude 7.5 earthquake could cause as much as $50 billion in damage in the Bay Area and up to $250 billion in damage in the Los Angeles Basin, according to estimates prepared by the risk consulting firm EQE International.

Even so, fewer people would be killed or injured, experts said, depending on the time of day and the epicenter of the quake. So far, the government of Turkey has reported more than 4,000 deaths and more than 18,000 people injured.

“We would not see casualties on this massive scale,” said USC earthquake geologist James F. Dolan, who had recently returned from a field trip during which he analyzed the fault system in Turkey. “What we can’t get away from is the economic impact of an earthquake.”

The quake in the heavily industrialized northwestern corner of Turkey was 10 to 15 times more powerful than the 1994 Northridge quake. U.S. scientists, who originally reported the quake in Turkey as magnitude 7.8, refined their measurements of the temblor to magnitude 7.4.

It was the seventh major quake on the same North Anatolian fault system since 1939.

In Southern California, there are at least six major fault zones that could theoretically cause an earthquake as powerful as that which rocked Turkey this week, including the Sierra Madre fault, the Newport-Inglewood fault, the Palos Verdes fault and the Hollywood-Santa Monica fault, which all bracket densely populated portions of the metropolitan region.

But in the aftermath of the quake in the region of Istanbul, most of the scientific attention focused on the similarities between the southern end of California’s San Andreas fault and the fault system that caused so much damage in Turkey.

The epicenter of the North Anatolian quake apparently was near Izmit, about the same distance from Istanbul as San Bernardino is from downtown Los Angeles.

The similarities were enough to send experts, including Dolan, from the Southern California Earthquake Center at USC and the Menlo Park, Calif., office of the U.S. Geological Survey, packing their bags Wednesday for Turkey.

The lessons in geophysics and earthquake geology they glean in Turkey will help make Southern California safer, they said.

“It is a horrific situation, but it is also a scientific opportunity to understand how earthquakes work, which will hopefully help us save lives,” said Dolan, who was coordinating a response team from the Southern California Earthquake Center scheduled to leave today for Turkey. “The more we can learn, the better we are armed to anticipate what can happen here.”

Next to the San Andreas, the North Anatolian fault is among the most well-studied in the world, and this newest quake offers regional earthquake researchers their clearest opportunities in recent decades to understand the physics underlying a major urban earthquake.

“This is a special earthquake,” Jackson said. “Big ones are rare, and we need to understand the big ones, so this is very, very important. It is in many ways like Los Angeles.”

The San Andreas and North Anatolian fault systems are long, relatively straight, strike-slip faults at the intersection of major tectonic plates on which earthquake energy is building up relatively rapidly.

Both systems are the “master faults” that dominate the geology of their densely populated regions.

The North Anatolian system, like much of the San Andreas, is a visible scar across the Turkish countryside, easily mapped and even more easily studied, Dolan said.

Both faults are adjacent to the deep echoing wells of major sedimentary basins that can amplify and redirect seismic shock waves. Los Angeles sits atop a bowl of sediments 30,000 feet deep. Istanbul is similarly situated, experts said.

A better understanding of how these basins can strengthen the powerful ground motions of an earthquake could help engineers devise better ways to withstand such severe, sustained jolts. The peak ground motions measured during the 6.7 Northridge earthquake, magnified by the megaphone effects of the L.A. Basin, were the most powerful on record.

“It is a very similar situation to what we might have,” said Lucille M. Jones, the U.S. Geological Survey scientist in charge of Southern California. “Let’s learn from their lesson. It is easy for us to discount it as happening in some Third World country, and that is a dangerous attitude.

“The amounts of shaking we would receive in our population centers would be similar, perhaps bigger.”

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How to Help

These aid agencies are among the many accepting contributions for assistance to victims of the earthquake in Turkey. For a more complete list, please see The Times’ Web site at https://www.latimes.com/turkeyaid.

American Friends Service

Committee

Turkey Earthquake Relief Fund

1501 Cherry St.

Philadelphia, PA 19102

Tel: (888) 588-2372

www.afsc.org

American Jewish World Service

Turkish Earthquake Relief Fund

989 Avenue of the Americas,

10th Floor

New York, NY 10018

Tel: (800) 889-7146

www.ajws.org

American Red Cross

International Response Fund

P.O. Box 37243

Washington, D.C. 20013

Tel: (800) HELP-NOW

Spanish: (800) 257-7575

www.redcross.org

Catholic Relief Services

P.O. Box 17090

Baltimore, MD 21203-7090

Tel: (800) 736-3467

www.catholicrelief.org

Lutheran World Relief

Turkey Earthquake Fund

P.O. Box 17061

Baltimore, MD 21298-9832

Tel: (800) LWR-LWR2

www.lwr.org

United Methodist Committee

on Relief

Turkey Earthquake Fund

475 Riverside Drive, Room 330

New York, NY 10115

Tel: (800) 554-8583

https://gbgm-umc.org/

units/umcor/

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Troublesome Tectonic Plates

Tuesday’s earthquake occurred on the North Anatolian fault zone, the source of numerous large quakes. The zone is susceptible to large tremors because it is near the boundary of two tectonic plates. Quakes occur as the plates slide past each other, as is the case along Californias San Andreas fault, where the North American and Pacific plates meet. Experts say the force generated by Tuesdays magnitude 7.4 quake was 10 to 15 times that of the magnitude 6.7 Northridge quake in 1994.