Wednesday, April 08, 2015

Hollywood Earthquakes

Next month, a new disaster thriller starring Dwayne “the Rock” Johnson will hit theaters, plunging audiences into chaos and destruction following a magnitude nine earthquake on the San Andreas fault. There’s nothing wrong with encouraging earthquake preparedness, but, as the new trailers make abundantly clear, San Andreas promises to be packed with far-fetched ideas about how earthquakes (as well as tsunamis) work.

To find out what Californians should and shouldn’t be worried about — and why — we spoke with Dr. Belle Philibosian, an earthquake geologist at the Institut de Physique du Globe de Paris, who studies the seismic potential of fault systems. Philibosian has seen her fair share of Hollywood earthquake myths, starting with 1978’s Superman, in which Lex Luthor attempts to trigger the San Andreas fault with a nuclear bomb in a sinister plot to create beachfront property in the desert.

“We wish that movies would get better,” she says, “but it seems like 30 or 40 years later, it’s still the same story.”

Movie tropes can affect the public’s perception of earthquake risk, and that’s no laughing matter, Philibosian argues.

“Either they’ll worry about the wrong things, or they’ll hear someone say, ‘This is completely ridiculous,’ and then maybe they won’t worry at all.”

Not worrying at all is not really an option for Californians. The San Andreas fault stretches across almost the entire length of California, and large, destructive earthquakes like the 1906 San Francisco quake and the 1989 Loma Prieta event have given the Golden State its seismic reputation.

Reiterating the need to focus on earthquake preparedness, the United States Geological Survey recently released an updated risk map for California that raises the odds of a large quake (magnitude 8 or greater) in the next 30 years from 4.7% to 7%. The increased probability is largely due to updated models that take into account the interconnectedness of faults, and the new numbers highlight the inherent difficulty in predicting the exact timing and location of large earthquakes.

They also make it clear that an impossibly large earthquake (magnitude 9 is just not in the cards for the San Andreas) on the most famous California fault isn’t necessarily the biggest threat to lives and infrastructure. For example, Hollywood might want to keep an eye on its own backyard, says Philibosian.

“If the fault underneath downtown Los Angeles had an earthquake, which would be nowhere near a 9 - the maximum is probably around 7 something - you could still end up with a scenario with collapsing high rises.”

San Andreas looks to be an action-packed disaster film, but if you want to know about the science behind the all-too-real danger, take a listen to the podcast before you head to the theater.

-Podcast and blog post by Meg Rosenburg

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