Is ‘San Andreas’ real? For starters, you can’t run in a major quake

The snickering could be heard as soon as the first teaser for the movie “San Andreas� was posted online.

Key plot points defy the laws of physics. An earthquake that opens up a canyon? Impossible. A San Andreas-triggered tsunami clobbering San Francisco? Please. A magnitude 9 earthquake in California?

Ha ha ha, say the earthquake experts.

“It’s a good action flick and spectacular special effects … but not realistic from a seismological point of view,� said Thomas Jordan, director of the Southern California Earthquake Center and USC professor.

A look at what’s true and what’s not as you watch the trailers and film, which opens on Friday:

Can California’s San Andreas fault really get magnitude 9 earthquakes?

No — the fault maxes out at magnitude 8.3, Jordan said.

Can the San Andreas create a tsunami that would inundate San Francisco?

No. The San Andreas is actually mostly on land. Big tsunamis are created by faults underwater.

The San Andreas fault is also vertical. So even when the San Andreas goes underwater, “it doesn’t move the ocean floor up or down very much,� Jordan said, which is needed to create a big tsunami.

Is such a giant tsunami plausible?

No. A big tsunami is 50 feet high, said U.S. Geological Survey seismologist Lucy Jones. In the movie, waves crash into the Golden Gate Bridge’s roadway, which is roughly 270 feet above the water.

Also — the break wave that you see in the movie as the tsunami comes ashore doesn’t happen. Tsunamis come in like a rising wall of water, not a surfing wave.

Can an earthquake fault create a canyon?

No. An earthquake is caused by friction, Jones said. Two blocks of earth need to move against each other to produce the shaking.

Can the East Coast feel a quake from California?

Nope. Even the great 1906 San Francisco earthquake was felt only as far away as Nevada, Jones said.

Can an earthquake in Nevada trigger a quake in L.A.? And can an L.A. quake trigger one in San Francisco?

Actually, yes. It’s happened the other way around. The 1992 Landers earthquake, a 7.3 in California’s Mojave Desert, triggered a 5.3 the next day in Nevada. And the great 1906 earthquake triggered magnitude 5 earthquakes the next day in Santa Monica, Oregon and Nevada.

Can big earthquakes hit Nevada?

Yes, Jones said. A magnitude 7 quake there is plausible.

Can you rescue a little girl off a crumbling Hoover Dam moments before it collapses in a giant earthquake?

Such a large quake depicted in the movie would knock you to the ground. As for the Hoover Dam, experts have studied it for seismic risk and concluded “the probability of failure is very remote,� said Ernie Hall, senior civil engineer for the U.S. Bureau of Reclamation.

What about other dams?

Other dams could be the problem. Three dams could begin to crack if a 7.8 quake hit the southern San Andreas fault, Jones said, referring to the USGS’ 2008 Shakeout earthquake scenario.

“It’s not that they would explode in the middle of the earthquake like we saw in the movie,� Jones said. More likely, it would be “bad-enough damage that would then allow water to seep through the cracks� and require evacuations.

The Van Norman Dam in Granada Hills was perilously close to collapsing after the 1971 Sylmar earthquake, forcing the evacuation of 80,000 area residents.

Lots of tall buildings collapse in this movie, including modern skyscrapers. Could that happen?

It’s actually the older, brittle concrete buildings that are the most dangerous, Jordan said. More recent modern high-rises are less likely to be a problem, he said.

The movie exaggerates the scale of destruction, said Farzad Naeim, a structural and earthquake engineer in Irvine and past president of the Earthquake Engineering Research Institute.

“You’re going to have pockets of destruction, pockets of collapse and casualties, but it’s not going to be Armageddon,� he said. “The toppling of buildings is very rare.�

Still, they’re expected to happen. The Shakeout simulation estimated that five high-rise steel-frame buildings could collapse after cracks form in connections in the building’s skeleton.

Are scientists close to predicting earthquakes?

No. The problem is that small earthquakes start the same way as large earthquakes, and small quakes hit all the time, Jones said.

What do experts and officials think about the movie?

Los Angeles Mayor Eric Garcetti said the most striking part of the movie “was the sense of complete panic that people have� in the moment the quake strikes.

Big problems will happen “if you aren’t practiced, and you aren’t prepared, and if you’re in denial that this is going to happen,� Garcetti said.

The mayor is leading an effort to require thousands of collapse-prone wooden and concrete buildings to be seismically retrofitted.

Naeim, the engineer, was critical of the film in making the earthquake so outlandishly over the top that viewers might throw up their hands and think there is nothing they can do to be prepared.

“I don’t think doing this overdramatization actually makes people prepared. I think it makes them passive.�

There are plenty of things that can be done. Retrofitting a house against sliding off its foundation would cost a few thousand dollars, a fraction of the cost of repairing damage. Owners can retrofit wooden apartment buildings. Even strapping bookshelves to walls and securing TVs and microwaves with Velcrostrips would save lives.

More information on preparing for a quake can be found at earthquakecountry.org.

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