Warner Brothers has just released the motion picture San Andreas, which portrays a major earthquake on the San Andreas fault, and its affect on California and elsewhere. The release of the movie, and the recent deadly earthquake in Nepal have many people thinking about earthquakes and how to prepare for the so-called “Big One”. So, in that sense, San Andreas is more than just escapist disaster-porn. It offers us a teachable moment, to separate the myths from reality about earthquakes.
It’s important to note that what makes an entertaining and dramatic disaster movie may not be reality. And there are several inaccuracies in the movie San Andreas that require clarification.
First, the strength of the ground shaking and the widespread collapse of buildings depicted in the movie is unrealistic. Modern building codes are designed to prevent buildings from collapsing during an earthquake. However, it is possible that some older buildings that were built prior to the establishment of modern building codes might collapse during prolonged, severe ground motions. On the positive side, the film’s hero – an LAFD Firefighter portrayed by Dwayne “The Rock” Johnson – orders people to Drop, Cover, and Hold-On, which is the recommended best practice during an earthquake to protect yourself from injury … no matter where you are.
Secondly, faults do not split apart, leaving a gaping chasm, as shown in the movie. In a strike-slip fault, such as the San Andreas Fault, the ground on the two sides of the fault slide past each; they do not pull apart. Crevices may form due to bends in the fault or in regions with very strong shaking. Also, contrary to what is mentioned in the movie San Andreas, any earthquake on the San Andreas Fault – no matter how large – would not be felt on the East Coast of the U.S. But a large San Andreas fault earthquake would be felt over a large region of California and neighboring areas, as was observed in the magnitude-7.9 San Francisco earthquake of 1906.
While a magnitude 7+ earthquake is possible in Nevada, there is no direct connection between faults located in the state of Nevada and the San Andreas fault in California. Still, large seismic events have occurred in Nevada in the 20th Century.
It is also important to note that — unlike in the movie, San Andreas — the San Andreas Fault cannot create a massive tsunami. While a part of the fault near and north of the San Francisco Bay Area is offshore, the blocks on either side of the fault slide past each other horizontally. This will not cause significant vertical motion of the ocean floor that is needed to create a widespread, damaging tsunami. In the movie, we commend the hero’s recognition of the onset of a tsunami-event. That was portrayed well, with Dwayne Johnson noting the drop/retreat of water-levels prior to the arrival of the tsunami, which allows people to take action to seek safety. Vertical evacuation, as shown in the film, is a good response. Still, many of the characteristics of the tsunami portrayed in the film are done for dramatic effect and are inaccurate. For example, a tsunami does not have a crest, and the water levels do not stay in place upon arrival.
It’s important to make a distinction between Hollywood fantasy and entertainment value and the reality of seismology and geology in California. There are commendable aspects of the movie’s depiction of “The Big One”, but, in the end, San Andreas is a movie, meant to make audiences gasp. If it also inspires us to get more prepared for an earthquake, then that could be its best contribution.
This document includes Key Message suggestions and Talking Points from the following agencies
Southern California Earthquake Center/Earthquake Country Alliance (SCEC/ECA)
US Geological Survey/California Geological Survey (USGS/CGS)
California Governor’s Office of Emergency Services (Cal OES)
Dwayne Johnson’s PSA for ready.gov.