Not just a movie: the facts on the San Andreas Fault
Not just a movie: the facts on the San Andreas Fault Dwayne Johnson, left, as Ray, and Carla Gugino as Emma, in a scene from the action thriller, "San Andreas" (- AP photos)
Not just a movie: the facts on the San Andreas Fault
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The San Andreas Fault awakens, unleashing back-to-back jolts that leave a trail of misery from Los Angeles to San Francisco. Skyscrapers crumble. Fires erupt. The letters of the iconic Hollywood sign topple. Tsunami waves swamp the Golden Gate Bridge.

Hollywood's favorite geologic bad guy is back in "San Andreas" a fantastical look at one of the world's real seismic threats.

The San Andreas has long been considered one of the most dangerous earthquake faults because of its length. At nearly 800 miles long, it cuts through California like a scar and is responsible for some of the largest shakers in state history.

In the new film, a previously unknown fault near the Hoover Dam in Nevada ruptures and jiggles the San Andreas. Southern California is rocked by a powerful magnitude-9.1 quake followed by an even stronger magnitude-9.6 in Northern California.

U.S. Geological Survey seismologist Susan Hough accompanied The Associated Press to an advance screening of the film. Despite the implausible plot, she said the San Andreas will indeed break again and without warning.

"We are at some point going to face a big earthquake," she said.

The San Andreas is notorious for producing big ones, but a magnitude-9 or larger is virtually impossible because the fault is not long or deep enough, Hough noted.

The 1960 magnitude-9.5 quake off Chile is the current world record holder.

The San Andreas has revealed its awesome power before. In 1906, a magnitude-7.8 reduced parts of San Francisco to fiery rubble. Nearly five decades earlier, a similar-sized quake rattled the southern end of the fault.

In 2008, the USGS led a team of 300 experts that wrote a script detailing what would happen if a magnitude-7.8 hit the southern San Andreas. They wanted to create a science-based crisis scenario that can be used for preparedness drills.

The lesson: It doesn't take a magnitude-9 or greater to wreak havoc. Researchers calculated a magnitude-7.8 would cause 1,800 deaths and 50,000 injuries. Hundreds of old brick buildings and concrete structures and a few high-rise steel buildings would collapse.

Computer models show the San Andreas is capable of producing a magnitude-8.3 quake, but anything larger is dubious.

In the film, Lawrence Hayes, a fictional seismologist at Caltech (a real university), notices spikes in "magnetic pulses" that light up California like a Christmas tree, heralding a monster quake.

Despite a century of research, earthquake prediction remains elusive. Scientists can't predict when a jolt is coming and are generally pessimistic about ever having that ability. Every warning sign scrutinized animal behavior, weather patterns, electromagnetic signals, atmospheric observations, levels of radon gas in soil or groundwater has failed.

"We wish it were as simple as the movie portrays. It isn't. Researchers have scoured every imaginable signal trying to find reliable precursors, but nothing has panned out," Hough said.

The latest focus has been on creating early warning systems that give residents and businesses a few seconds heads up after a quake hits, but before strong shaking is felt.

Japan has the most advanced seismic alert system in the world while the U.S. is currently testing a prototype.

Unlike the film, the San Andreas can't spawn tsunamis.

Most tsunamis are triggered by underwater quakes, but they can also be caused by landslides, volcanoes and even meteor impacts.

Giant tsunami waves are formed when the Earth's crust violently shifts, displacing huge amounts of seawater. The larger the magnitude, the more these waves can race across the ocean without losing energy.

The San Andreas is a strike-slip fault, in which opposing blocks of rocks slide past each other horizontally. A big San Andreas quake can spark fires and other mayhem, but it can't displace water and flood San Francisco.

Hough said the movie got one aspect right: The tide suddenly ebbing out signals a tsunami is coming.

More than 80 mostly small tsunamis have been observed along California's coast in the past, triggered mainly by faraway quakes.

In the movie, the scientist warned that shaking would be felt on the East Coast. But even the largest possible San Andreas quake won't rattle the East Coast (sorry, New York).

While seismic waves from great quakes can make the Earth reverberate like a bell, the ringing can only be detected by sensitive instruments because it's so low.

Historical accounts show shaking from the 1906 San Andreas quake was barely felt in western Nevada and southern Oregon, Hough said.

When the ground starts to shake, the seismologist played by Paul Giamatti makes the ideal public service announcement: "Drop, cover and hold on."

Since 2008, millions of people in California and elsewhere have participated in yearly disaster drills in which they practice diving under a table and learn other preparedness tips.

If you're outdoors when the ground moves, experts recommend bracing against a wall, similar to what search-and-rescue helicopter pilot Ray Gaines, played by Dwayne "The Rock" Johnson, told scared survivors in the movie.

Critical thinking challenge: Why can't the San Andreas fault cause a tsunami that drowns California?

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Assigned 30 times

  • 1CoraA
    5/29/2015 - 10:43 a.m.

    before reading this article i didn't know that the san andreas was a real thing! i didnt know either that they based this movie about what really happened at san andreas.

  • 5AudreyT
    5/29/2015 - 12:18 p.m.

    5 Ws
    Scientists have been comparing the real San Andreas fault to the movie. In 1906 an earthquake with a magnitude of 7.8 occurred nears and around the fault. The movie, however, portrayed it to be a 9+ magnitude of an earthquake which is the equivalent of the world record earthquake of 9.5 in Chile. Scientists say that the fault is only capable of an earthquake up to a magnitude of 8.6 and contrary to the movie, it would not be felt on the east coast. Even in the 1906 earthquake, the shakes were barely felt in southern Oregon. The United States is currently working on a prototype alarm system to warn people of an oncoming earthquake, and is hoping to train citizens near the fault what to do in the event of an earthquake. Another earthquake around the fault is expected, so people should be prepared.

  • 5IzabellaP
    5/29/2015 - 12:22 p.m.

    We could all learn a lesson from this. Not all movies are fiction. Yes there might be Historical movies and what not, but it is very rare to go to a movie that is fictional be based on a true event. There are few movies that do this, but they are still very good to watch even if it is a horror, action, comedy, romance, etc. Most of the time when you go see a action movie for example, you expect it to be fake and not based on a true story. But in this action movie it is based on a true event that had happened in life a while back. So what we have to look for is if it was or is based on a true story.

  • 5AllyR
    5/29/2015 - 11:29 p.m.

    I hope that this movie is as good as it sounds and seems. I like that it is based off of a real event and has an action packed twist with lots of drama. I'm actually looking forward to seeing this movie which I hope I do see it. The previews looked really good and intense. I also hope everyone understands the feeling of what it's like in an earthquake.

  • 1GeorgeB
    5/30/2015 - 07:25 p.m.

    The reason why the San Andreas fault can't cause a tsunami is simple it's location and what kind of a fault it is. Why, the reason why the San Adreas can't produce a tsunami is because it is not under water. For a fault to trigger a tsunami, it needs to be underwater so that when an earthquake happens, it can displace water which in turn produces a tsunami. But this is not the case for the San Andreas, the San Andreas is located under land therefore eliminating the chance of it producing a tsunami. The second reason why the San Andreas fault can't trigger a tsunami that would drown California is because it is a strike-slip fault. a strike-slip fault cannot create a tsunami because it is two plates running against each other, not going head to head which would be able to produce a tsunami.

  • 1AbbyP
    5/31/2015 - 01:36 p.m.

    Misery from Los Angeles to San Francisco letter from the Hollywood sign crumble and the golden gate bridge Is attacked with tsunami waves. San Andreas fault is called the most dangerous fault in the U.S.It hit with a 9.1 for the magnitude. While they were filming the ground started to shake.SInce 2008 California has been practicing its drills they say to go under a table or if you're outside stand by a wall.

  • caoilinncrotty53
    6/01/2015 - 01:14 p.m.

    The San Andreas fault can't drown California because the San Andreas is a transform fault, which means that the plates side along each other and don't crash into each other. The plates sliding along each other makes the waves just move around a little, but if the plates were hitting each other it would make a tsunami on our shore, thankfully, the plates don't hit each other.

  • jacobfrancel46
    6/01/2015 - 01:18 p.m.

    Wow, that is really scary that a 8.3 earthquake could hit at anytime and wreak havoc. Also, in 2015 there have been a lot of larger earthquakes popping up, almost a couple a month. I did some research and found that the San Andreas Fault is actually quite dangerous because the world's plates are moving and causing a lot of shaking. On 5/30/15 there was an earthquake in Japan with a 7.8 magnitude. On 6/1/15 there were 5 earthquakes in Oregon the highest magnitude was 6.0. There have been 17 large earthquakes in the world from 5/3/15 - 6/1/15, with magnitudes 3.3-7.8. This is really scary!

  • IvanMTeal
    6/02/2015 - 12:45 p.m.

    WOW. Thats amazing and not cool at the same time. But I really hope that it does not happen again, even tho it says its gonna happen again, but lets just hope its not!

  • Codyh-Lam
    6/02/2015 - 01:32 p.m.

    I didn't even hear about San Andreas until the movie came out. It is interesting to learn about the fault, and disappointing that the movie is so unrealistic. I still want to see it, though.

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