I managed to catch the new movie ‘San Andreas’ last night – perfect timing for a unit of work I had just started with year nine students, looking at earthquake preparedness in California.
It is a classic American ‘action movie’, and if you can tolerate the weak script and clichéd drama – the 3D special effects come to the fore, and very impressive they proved to be.
A number of my students had either already been to see the film, or were planning to over the next few days – and it was pleasing that much of the content was actually accurate and directly relevant to the work they were doing in class. The San Andreas Fault system was obviously highlighted, but there were also good references to seismologists, plate tectonics and some coverage of the earthquake history in this dynamic part of the world. There were also mentions of the Moment Magnitude measuring scale, as well as some reference to rebuilding after a natural disaster in an MEDC. I particularly liked the coverage given to earthquake drills such as ‘duck, cover and hold’ as well as one scene where the lead actor ‘The Rock’ (who was actually very good, I thought, despite the poor material he was given to work with) encouraged a group of citizens to brace themselves against a solid wall to avoid flying debris.
However, watching as a geographer, there were also many inaccuracies that were given film license. I promised Mrs B I would not harp on about these on the journey home after the film, but I feel I need now to get them off my chest.
First of all, let’s deal with the main premise of the movie – that an earthquake of M 9.1 has shaken California, and a further 9.6 earthquake was on its way. Although this region surely faces the impact of a potentially large ‘quake in the short-term future, earthquakes of the size suggested in the film could certainly not be generated from the plate dynamics here. The San Andreas system is noted for producing large earthquakes in the past, but a magnitude 9 or larger is virtually impossible because the fault system is not long enough or deep enough. In the film, the entire fault ruptured from Mexico to Oregon, and this kind of event has never been seen before, and is a highly unlikely scenario for the future. The most powerful ‘quakes recorded in history have struck along offshore subduction zones where one tectonic plate dives beneath another (the 1960 magnitude 9.5 earthquake off Chile is the current ‘world record holder’, and did get a mention in the film). Modern computer models show that San Andreas is capable of producing a magnitude 8.3 earthquake, but anything larger is dubious.
Next, the tsunami. Although there was a nice mini-scene where ‘The Rock’ spotted the tide receding, and correctly identified this as a warning sign of a tsunami – the San Andreas cannot spawn these giant sea waves. Most of the San Andreas Fault is landlocked, and where it heads offshore, it occupies only shallow waters. In the 1906 earthquake, a less than half a metre wave was generated. Landslides resulting from the Santa Barbara ‘quake of 1862 did produce a tsunami of several metres in height – but this nowhere near matches up to the mega-tsunami in the movie that destroys the Bay bridges and flips container ships onto the shore. Most tsunamis are triggered by underwater ‘quakes that lead to giant sea waves formed when the Earth’s crust violently shifts to displace huge volumes of seawater. The San Andreas is a strike-slip fault, where opposing blocks of rock slide past each other horizontally. A big San Andreas ‘quake can spark fires and cause building collapse, but it could never displace water and flood San Francisco Bay! The numerous small tsunamis that have been recorded in the past along the Californian coast have been mainly triggered by far away tectonic events, and the threat from local events is not significant.
To portray the aftermath of the major earthquake, the film showed giant fissures appearing in the ground that swallowed up cars, people and whole buildings. Most earthquakes that cause ground rupture do have associated tension cracks that can, at times, get large enough to place an arm into – but the giant chasms of the film would not be realised.
There were some brilliantly made images of collapsing skyscrapers in the film – but it is more likely that they will remain intact due to the high technology foundations and structures employed in their construction. Even in the recent Nepal earthquake, where poor standard construction was common, destruction looked nothing like that shown in the film. Most damage in any future Californian earthquakes will more likely focus on unreinforced masonry and soft-storey buildings, not the modern ones which will shake, rattle and sway – but not necessarily tumble down.
Some of the most dramatic special effects in the film depicted the collapse of the Hoover Dam because of earthquake activity. Could a large earthquake in Nevada trigger the San Andreas system into action to destroy the dam? There are certainly fault lines in this region that are capable themselves of generating earthquakes in excess of M 7.5, but they are nowhere near the dam itself. It is extremely unlikely that any disturbance to the San Andreas system would result in serious damage to the far away Hoover Dam.
One underlying theme in the movie was the work of the scientists at Caltech (a real university) who had successfully developed methods to accurately predict tectonic events. Although, we might accept that we need to listen carefully to scientific research, even the richest and most technologically advanced nations are still a long way from accurate and reliable earthquake prediction. All possible warning signs – including animal behaviour, weather patterns, electromagnetic signals, atmospheric observations, levels of radon gas in soil or groundwater – have failed, and scientists are generally pessimistic about ever having the ability of earthquake prediction. The latest focus in high risk areas has been to create early warning systems that give a few seconds’ warning before the strongest shaking is felt by residents.
Another fallacy in the film was the suggestion that the Californian quake would release so much energy, it would be felt in New York City. Even the largest San Andreas shaker would not rattle the east coast of the USA! Historic accounts show that shaking from the huge 1906 San Andreas ‘quake was barely felt even in nearby western Nevada and southern Oregon.
So, ‘San Andreas’ is certainly a treat for fans of CGI graphics and special effects, and the geographical theme makes it a ‘must see’ for budding seismologists. Interestingly, on May 29th of this year – the same day the film was released – a M 3.8 earthquake was reported near Indio in California. So whatever the scientific flaws of this movie, at least it might remind us of the potential reality facing this part of the world. If nothing else, the film might rekindle a serious public conversation about the possible consequences of a large earthquake in modern America, and how best people might prepare for it. Check the movie out, and let me know what you think.
Tomorrow, it’s time for ‘Mad Max’ – and I will probably have to think water issues or recycling themes if I am to connect it to next week’s geography lessons!