‘San Andreas’ movie destroying S.F. is great fun, bad science

This photo provided by Warner Bros. Pictures shows Paul Giamatti as Lawrence and Archie Panjabi as Serena, in a scene from the action thriller, "San Andreas." The movie releases in theaters on May 29, 2015. (Jasin Boland/Warner Bros. Pictures via AP) less This photo provided by Warner Bros. Pictures shows Paul Giamatti as Lawrence and Archie Panjabi as Serena, in a scene from the action thriller, "San Andreas." The movie releases in theaters on May 29, 2015. ... more Photo: Jasin Boland, Associated Press Photo: Jasin Boland, Associated Press Image 1 of / 34 Caption Close ‘San Andreas’ movie destroying S.F. is great fun, bad science 1 / 34 Back to Gallery

The latest Big Disaster movie is wiping out San Francisco this week as a monster earthquake and tsunami swallows the city and drowns the Golden Gate Bridge — all in less than two hours on the silver screen.

To the real experts on quakes and their effects — the geologists and emergency specialists who watched it at a Friday night showing sponsored by the city’s Office of Emergency Services — the film is a hoot, and crammed with more ersatz seismic science than Hollywood has ever before conjured up.

But the experts loved it and laughed as the movie’s star, chief firefighter Dwayne Johnson (the Rock), wrestles with his official helicopter, steals a pickup truck, flies a fixed-wing plane and finally uses a million-dollar speedboat to outrun a tsunami’s smashing crest and find safety beyond Mile Rock.

“But he’s headed the wrong way,” geophysicist Ross Stein of the U.S. Geological Survey said with a laugh. “He shouldn’t try to beat a tsunami — he should turn the boat around and head inland into the nearest slough. It’s calmer there.”

Too big for fault

And a really big tsunami is impossible in California, Stein said, because the San Andreas is what geologists call a strike-slip fault and it would inevitably rupture sideways in a real earthquake; it couldn’t do more than make ripples, except perhaps in a harbor, Stein said.

But the film’s “biggest blooper,” he said, is giving a magnitude of 9.6 to the quake that topples every skyscraper in San Francisco, destroys Los Angeles, and opens a horrendously deep chasm across the verdant landscape while frightened hordes flee crashing buildings in both cities.

“Too big for a real San Andreas fault,” Stein said, “and only a subduction zone quake like the ones in the Pacific Northwest and Alaska could open even a small rift in the ground — certainly not a huge canyon around here.”

That wasn’t the only howler Stein found as he searched the credits vainly for the names of the film’s science advisers. “They’re probably in hiding,” he said.

Stein did credit the movie’s writers for giving Paul Giamatti, as the wise Caltech scientist, the good sense to voice the only sensible words in the script: “Duck, cover and hold on,” he tells his crouching colleagues as debris rains down and Caltech’s buildings are flattened. “Duck, cover and hold on,” he repeats to a few neighbors.

And when the plucky teen-aged heroine, a terrified Alexandra Daddario as the Rock’s daughter, is trapped inside a shuddering highrise in the Financial District (with an impossible view of the doomed Golden Gate Bridge), her new boyfriend’s younger brother happily comes upon a storage cooler crammed with bottled water.

That, at least, was a sensible bright spot in the movie, said Amy Sinclair of the San Francisco Public Utilities Commission. She’d brought along a huge bottle of water to make her pitch for what every family should stock up on before a real quake.

“You can get along for three days or more without food,” Sinclair said, brandishing her bottle like a talisman, “but you’ll need water a lot sooner. So clean out lots of old bottles and your fresh water will keep for six months before you refill.”

Running in wrong direction

To Kate Long, head of the Earthquake and Tsunami Program in the Governor’s Office of Emergency Services, all the film’s fleeing folks in San Francisco are running the wrong way as buildings topple and the tsunami floods the streets.

“If you’re running close to the coast, the smart thing is to head for higher ground,” Long said. “And in San Francisco it’s so easy — just walk up any hill.”

But the movie’s on the right track, Long said, as she offered kind words for the Rock’s determination to rescue his ex-wife and his daughter, plus the daughter’s friends who survive every gut-wrenching peril.

“Yes, it’s crucial for families to stick together in an earthquake,” Long said, “and it’s good that the movie stresses togetherness.”

Stein lost track of the film’s scientific bloopers: The 7.0-magnitude quake that destroys Hoover Dam near Las Vegas is rupturing the earth in a region where even small faults are few and far between, he said.

And serious scientist Giamatti is way off base by actually predicting the monster quake on the movie’s San Andreas fault, based on strange electromagnetic pulses he detects deep inside the ground.

“But people are really afraid of earthquakes,” Stein said, “and if a movie like this one goes over the top it might help exorcise those fears, so maybe that’s a good thing. And this one is certainly over the top.”

David Perlman is The San Francisco Chronicle’s science editor. E-mail: dperlman@sfchronicle.com Twitter: @daveperlman