Along with the stories of tragedy in Italy, there are also stories that the earthquake was predicted, and that the predictions were ignored. Was the tragedy made even worse by authorities who wouldn’t listen to a scientist who knew what he was talking about?
Now, I’m not a seismologist, but I know a little about predicting earthquakes. I predicted one, you see: the 1989 Loma Prieta earthquake.
There had been a small earthquake just before I arrived at Stanford, so earthquakes were on a lot of people’s minds. The San Francisco Examiner had a hilarious cartoon about how to use your pet to determine the size of an earthquake, Stanford was distributing what-to-do-in-an-earthquake pamphlets, and geology grad students were making bad jokes. When I heard that the San Francisco Giants and the Oakland A’s might be in the World Series, I said “wouldn’t it be great if SF played Oakland, and there was an earthquake?”
And that’s how I predicted the 1989 World Series earthquake.
Now, before you read any further, a quick quiz: what was wrong with my prediction?
Now, there aren’t any reasonable mechanisms by which baseball can cause earthquakes. On the other hand, Giampaolo Giuliani used measurements of radon gas. Radon is produced as part of the decay series of uranium, and is found trapped in soils and rocks. It’s possible that it could be released in the lead-up to an earthquake, according to some models of how ruptures begin. (If ruptures begin with micro-cracks forming, they might increase the permeability of the rock, and allow more radon to move towards the surface.) Radon was one of many earthquake precursors that have been studied since the 1970’s, in hopes that some reliable precursor might be found.
None of those precursors have turned out to be reliable. Not radon, not groundwater levels, not ground inflation. Foreshocks, maybe – sometimes there are smaller earthquakes before a larger earthquake. But there are also small earthquakes without larger earthquakes, all the time.
Studies of earthquake behavior, including events that may make an earthquake more likely, continue. Maybe at some point seismologists and structural geologists will understand what happens before an earthquake, and then we will really be able to forecast them. (Or at least say that they have become more likely, as volcanologists do with eruptions. I don’t know whether earthquakes warnings will ever be as good as flood warnings or hurricane warnings.)
But even if our understanding does increase, it’s worth keeping in mind what would be necessary for an earthquake prediction to be useful. There are several questions that are traditionally asked:
- Where will the earthquake occur?
- How big will the earthquake be?
- When will it happen?
Reliable answers to those three questions are important if emergency planners are going to ask people to change their behavior. Small earthquakes occur every day, somewhere in the world. Earthquakes only affect people who live near them, and only the larger earthquakes are destructive. And if you’re going to tell people to get out of their houses, you’d better have some idea of when they will be allowed to go back when nothing happens.
It’s that last point, the timing of the earthquake, that is the biggest problem for Guiliani’s prediction of the Italian quake. According to some news reports (80 Beats, LA Times), Giuliani’s prediction was for a 24-hour period last week (March 29, to be exact). Even if Giuliani’s radon measurements were related to this week’s quake, his prediction technique got the timing wrong. [Edit: Apparently, he also got the place wrong: his prediction was for an earthquake 30 km away, in Sulmona. See more at olelog and, if you read German, at Amphibol. According to the USGS map of estimated shaking, the shaking 30 km away from L’Aquila was only Mercalli intensity V – unlikely to destroy buildings and kill people. So that’s two things wrong. As Ole says, what if people in Sulmona had heeded the warning… and evacuated to L’Aquila?]
If I were teaching The Control of Nature this week, I would turn this into a discussion. Giuliani is working with a technique that hasn’t been very successful in the past, and which has mostly been discarded in favor of other earthquake research. But he still thinks it works. So what are the ethical obligations of a scientist in this case? Should one go public with warnings, given the risk that they may be false alarms? Is it worse to create unnecessary panic, or to have people die in the earthquake? (What are the chances that the panic itself would result in deaths, from traffic accidents or from a lack of shelter on cold nights?) In Giuliani’s case, Reuters reports that vans with loudspeakers were driving around L’Aquila, telling people to evacuate… a month ago.
I don’t have an answer to that question.
(Oh, and for people wondering what was wrong with my 1989 “prediction,” apart from the absurdity of relating baseball to earthquakes: if a magnitude 2 earthquake had occurred in Japan during the World Series, could I have claimed a successful prediction?)
A few other discussions of Giuliani, from both blogs and the mainstream media:
LA Times: Did Scientist Predict Italy quake? (Includes good discussion of earthquake prediction history and current direction by seismologists from southern California.)
Other info on earthquake prediction: