As an earth scientist and a science educator, I cringed when I saw, many months ago, a trailer for the new film San Andreas. The movie opens tomorrow, and judging by the pre-release media, the movie is replete with scientific errors.
Movies can shape the perceptions of students. Bad movies can create misperceptions in students which are very, very hard for science educators to counter. Geology has been particular hard hit by Hollywood with a string of awful, scientifically-abominable movies such as The Core, Volcano, Dante’s Peak, The Day After Tomorrow. These films often took a kernel of truth–yes, fresh water surges from melting Greenland may change North Atlantic circulation patterns and decrease temperature, as is the case for Day After–and blow it up into a ridiculous fantasy. Such distortions of science are completely unnecessary, too, because the story of the plain facts is amazing enough and doesn’t need embellishments to be entertaining.
When the real San Andreas fault goes, it’s going to kill a lot of people, separate a lot of loved ones, cause waves of grief and suffering. Just the plain story would make a fine movie. So what Hollywood has instead done is decide that viewers are fools who can only be entertained by tripe gussied up with explosions. In service of this distortion, Hollywood has created a monstrosity. I expect that years from now I will have students ask question based on the San Andreas movie–just as I do for The Core, The Day After Tomorrow, and so on.
What’s wrong with the San Andreas movie? Let me count the ways:
Error: The trailer shows this crack in the earth, suggesting that the San Andreas fault has opened up the ground maybe 20 meters across.
Fact: Faults do not open up the ground in this way, with a gaping hole leading down to nothingness. Though they may distort the surface, rarely is there a gap of more than few inches created even by the largest quakes. In fact, we know what the San Andreas fault does to the ground in big quakes, because after 1906 a photographer named Grove Karl Gilbert recorded images such as this:
There’s not really any “gap” here, despite the high magnitude of the quake. So I’m sure that after this movie comes out, future students will now expect several meter gaps from large quakes and want to know what was wrong with 1906.
Error: The quake affects both LA and San Francisco.
Fact: The San Andreas is not one continuous crack, but rather a system where stress builds up and then is released, usually in discrete, limited sections. Though both Los Angeles and the San Francisco Bay Area have many quakes every day, these quakes are not connected in any direct way.
Error: A lot of structural damage occurs in the movie.
Fact: In 1906, most of the non-earthquake resistant buildings in SF came through the quake just fine. With today’s earthquake retrofitting and increased engineering knowledge, even fewer structures (as a proportion) would be damaged by a large quake. So the trailer seems to show utter devastation, skyscrapers falling on their sides. Nonsense. The worst that is likely to happen to skyscrapers is that they will be so damaged as to become uninhabitable; total collapse is very unlikely.
In 1906, the fire did far more damage to SF than the quake itself. This still from the trailer seems to show numerous fires, so in that respect it follows what might happen. But skyscrapers falling out of the sky? That’s dramatic–but wrong.
Error: Hollywood is probably going to call this a 9 or 10 on the Richter scale, when we in fact would use the moment magnitude scale (Mw).
Fact: The San Andreas simply can’t produce quakes of that size. There are fault zones that can produce such monsters–the Cascadia fault zone off Oregon and Washington, for example. But such quakes involve subduction zones, where an oceanic plate pushes underneath a continent. That violent process involves tremendous friction and pressure and yields the biggest, deepest quakes we know.
That’s not what’s happening with the San Andreas. The San Andreas involves two continental plates grinding past each other, and produces relatively shallow quakes (the average depth being just 15 km).
The dynamics for the San Andreas are such that when enough stress builds for a ~Mw 8 quake, that’s about all the rocks can take and they break. So we can certainly get Mw 8s. But Mw 9s are extremely unlikely, simply because the rocks themselves cannot hold this kind of energy.
So when the San Andreas eventually goes–as it must–it will be bad. But not this bad.
Error: A giant tsunami approaches San Francisco. Its height appears to exceed the roadway of the Golden Gate Bridge, which is 67 m, so we can judge the tsunami to be over 100 m high.
Fact: There are two major problems with this. One, tsunamis tend to be far smaller than this, often no more than a meter or two. The image of a giant, horizon-occulding wave is a myth created by Hollywood because it looks more dramatic. (Google for videos of Indonesia in 2004 to see just how dramatic and deadly the reality of a 1 m tsunami can be.)
Second, the San Andreas is very unlikely to produce tsunamis at all. What we need to create a big tsunami is a subduction zone quake where one side gets lifted up or dropped down several meters. Essentially the entire column of ocean water is moved all at once. That energy then spreads out in either direction perpendicular to the fault and where it intersects with land, surges on land in what often looks like a temporary elevation of sea level.
There’s not really any way for the San Andreas to move the ground in a way that would raise or lower the ocean column. In fact, the waters where the San Andreas cuts past San Francisco are only a few hundred feet deep, so even if it did lift up, it wouldn’t move that much water and thus wouldn’t create a big tsunami.
Maybe Hollywood is implying part of the continental shelf breaks loose and surges into the Pacific; that could conceivably happen (and we worry about similar situations in the Canary Islands). But if that happened, it would seem that the tsunami would go the other way, toward Hawaii and Japan.
In summary, the new movie San Andreas is likely to do a serious disservice toward the public understanding of science. And the effects of this movie will likely last a long time, influencing many students and hurting their chances of understanding a key phenomenon of our active world.
Sadly, these distortions are unnecessary. Nature is violent and dramatic enough to stand on its own, without Hollywood embellishment. Perhaps some day there will be an honest science movie, but that is not this day.