San Andreas movie – fact check

San_Andreas_posterTomorrow is the release of the latest disaster film, “San Andreas” starring Dwayne Johnson aka The Rock.  This time his character, a search-and-rescue helicopter pilot must save his daughter after a major earthquake wreaks havoc from Los Angeles to San Francisco. In the film, an unknown fault ruptures and triggers the San Andreas that sets off a 9.1 earthquake in Southern California and is then followed by a stronger 9.6 in Northern California.

This film begs us to ask the question – is this possible? How accurate is the movie?

Our friend, Dr. Lucy Jones, U.S. Geologic Survey seismologist, was on hand at the films screening and separated fact and fiction with live tweets from the films event. Lucy did praise the film’s portrayal of emergency response and the use of “drop, cover and hold on” – a safety practice we should all be very familiar with.  Since 2008, millions of people across the world have participated in the annual Great ShakeOut earthquake drill, practicing this safety activity.

But Dr. Jones also stated that the movie stretched into “fantasy territory”. So let’s talk about what was made for the movies.

A 9+ magnitude earthquake out of the San Andreas

While the San Andreas is known as one of the most dangerous earthquake faults and has a history of producing significant earthquakes, a magnitude 9 or larger is highly unlikely.  Computer models have shown the fault is capable of a magnitude 8.3 earthquake – anything large is extremely unlikely. The fault is not long enough or deep enough.

However, it is important to note that it doesn’t take a magnitude 9 to cause destruction. In 2008, the USGS led a team of experts that scenario’d a magnitude 7.8 hitting the southern San Andreas. The researchers calculated that a 7.8 would cause 1,800 deaths, 50,000 injuries and hundreds of old brick buildings and concrete structures and a few high-rise steel buildings would collapse.

Earthquake prediction

In the film, a seismologist notices spikes in a magnetic pulses in California – “predicting an enormous earthquake”.

Despite years and years of research, scientists can’t predict when a quake is coming. The USGS states that “there is no scientifically plausible way of predicting the occurrence of a particular earthquake”. However, 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. Allowing for the opportunity to for some to get quickly out of harms way.

A tsunami drowning San Francisco

Could the San Andreas produce a tsunami that would take out San Francisco? In short, the answer is no. A big San Andreas earthquake could spark fires and other pandemonium, but it can’t displace water and flood San Francisco.

The USGS states that the “San Andreas fault cannot create a big tsunami”. Most tsunamis are triggered by underwater quakes on “subduction zone faults, on which [a] fault slip cause[s] vertical uplift of the sea floor”. The San Andreas is a strike-slip fault, in which opposing blocks of rocks slide past each other horizontally. “While a part of the San Andreas Fault near the north of San Francisco is offshore, the motion is mostly horizontal, so it will not cause large vertical motions of the ocean flood that would generate a tsunami”.

“Earthquakes on other faults offshore California as well as underwater landslides triggered by strong shaking can create local tsunami, some of which maybe locally damaging.”

A large San Andreas earthquake shaking the East Coast

In the movie, a scientist warns that shaking would be felt on the East Coast. But even the largest possible San Andreas earthquake wouldn’t shake the East Coast. Historical records show that the shaking from the 1906 San Andreas quake was barely felt in western Nevada and southern Oregon.

Learn more about Earthquake Facts & Earthquake Fantasy from the USGS.

In summary, don’t learn about earthquakes watching the “San Andreas” movie; take it for its entertainment value. But learning more about earthquake preparedness is key to earthquake survival. Seismologists do agree that the San Andreas will indeed strike again, and without warning.  We are at some point going to face a big earthquake and we need to be prepared.

Posted in Earthquakes, fact vs fiction, USGS
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