Science a bit shaky in earthquake movie 'San Andreas'

San Andreas, the new disaster movie opening Friday, features gigantic earthquakes ripping California apart. But don't count on a lesson in accurate science.

"Don't consider this your seismology course," said U.S. Geological Survey seismologist Lucy Jones, who previewed the movie this week in California.

Filled with typical Hollywood over-the-top exaggeration, it was "a lousy documentary but a good movie," Jones said. "It was better than I thought it would be."

What did it get wrong? Plenty, she said.

The movie features magnitude-9.6 and -9.1 earthquakes in California, which can't happen along the San Andreas fault, Jones said. A magnitude-8.3 quake is the upper limit that can occur along that fault, she added. Worldwide, the strongest quake ever measured was the magnitude-9.5 quake that hit Chile in 1960.

In addition, the movie features a giant quake-caused tsunami, which isn't possible on the San Andreas fault line because it is on land. An oceanic quake is needed to cause a tsunami.

The movie tsunami, which crashed over the Golden Gate Bridge, also was way too big. "You can't get a tsunami bigger than the ocean is deep," Jones said.

Other quibbles: Earthquakes can't be predicted and buildings don't explode in quakes (they collapse).

Still, Jones said there were a couple of things moviemakers got right: One earthquake can trigger another nearby, and the aftershocks in the movie were realistic.

The movie also detailed the correct actions people should take when a quake happens: "Drop, cover and hold on."

Movies are ultimately about emotions, and Jones said the filmmakers really captured that, especially the feelings of separated family members. "Not knowing if your family is OK is hard," she said. Jones said she hopes the film will spur families to develop a communication plan in case of a disaster.

San Andreas, which stars Dwayne "The Rock" Johnson, opens Friday nationwide.