Could listening to earthquake predictions have saved lives in the Abruzzo region of Italy? Lars Ceranna of the German Federal Institute for Geosciences and Natural Resources (BGR) explains why it’s still impossible to predict earthquakes, and what to do when one occurs.
 | Lars Ceranna, German Federal Institute for Geosciences and Natural Resources (BGR)"It will take weeks until this area is seismically inactive, at least to a certain degree." (Photo: Ceranna) |
What causes an earthquake?
The earth we are living on is a very dynamic planet. The tectonic plates on the surface of the earth are moving, up to a few centimeters per year, and some of them are colliding. When this happens stress is accumulated. Sometimes this stress release is so high that it produces a friction in the plates and this, in essence, is the earthquake.
In Italy, we have Africa and Europe colliding, and this causes stress. It is actually a little bit more complicated, we have several other micro-plates in-between these two big ones, but in essence, this is the cause for the latest earthquake. The collision of Africa and Europe has also formed the Apennines, the mountainous region where the earthquake occurred.
Apparently there were warnings of a major earthquake before Italy was struck. How reliable are such predictions?
I think everyone in the seismological community would agree that earthquake prediction is impossible. At the moment, we are not able to predict earthquakes; it is just too complicated. Earthquake prediction is defined by three variables: you have to say when an earthquake will occur, where it will hit, and what strength it will have. And this information has to be precise. We are talking about plus minus ten or twenty kilometers, the date should be plus minus one day and the strength should cover a range of plus minus 0.3 magnitudes.
This is still impossible. We have not fully understood what is going on in the earth and what exactly might cause earthquakes. Of course, we have an idea, but this is more or less a mathematical and physical model. It is impossible for us to see into the earth; it is a solid medium and not glass.
What you can measure, however, is the risk of an earthquake striking a certain area. How is this done?
This is simpler. We assume that earthquakes have something that is called recurrence time. You collect all information of past earthquakes and, judging from these, estimate the seismological risk in a given area. What you will learn from that is what magnitude of an earthquake will occur with a certain probability in the area you are interested in. The basic assumption is that earthquakes are a recurring phenomenon.
How likely are further earthquakes in this part in Italy?
There will be, of course, some aftershocks; some of these may have magnitudes up to five (on the Richter Scale). It will take weeks until this area is seismically inactive, at least to a certain degree.
Looking at Europe, where are other danger zones?
Of course, Italy is one of the most prominent seismic region in Europe. The other one is the Aegean comprising both the subduction of African under Europe, which stretches from Rhodes to Crete and the Peloponnese, and the Anatolian transform fault crossing Istanbul and going to Athens and the Graben of Corinth.
Nevertheless, a major earthquake in Western or Northern Europe is unlikely, but not impossible. There are scenarios for a magnitude 6 earthquake in the area of Cologne. Not so long ago, in 1992 there was a 5.9 earthquake in the Dutch town of Roermond, which is close to Cologne.
How can individuals protect against an earthquake?
Well, the most important thing is to adhere to building codes. I think most countries have strict codes, and if you follow these, you are more or less on the safe side.
During an earthquake, the best idea is to protect yourself by hiding under a table or a doorframe, because a lot of things will fall down. If you are on the ground floor close to the entrance, you can try to run outside, but once you feel the tremor, it is usually too late and you would jeopardize your life if you try to run down the stairs during an earthquake.
What is really paradox is that older buildings made out of wood often do much better during an earthquake than modern buildings from the 60s and 70s. The problem is that engineers are often very good with statics, but an earthquake is a highly dynamic event and equations on the necessary static of a building just don’t work anymore when the ground is moving in all directions. Old houses from medieval times often do so much better because the wood is more flexible than concrete, and they have so many diagonal structures that protect the house even against strange movements.
Is there something governments can do to minimize risks?
Well, Japan has developed some interesting tools to better deal with earthquakes. They were the first to come up with some sort of earthquake warning system and mitigation strategies.
It is all about how to best protect urban centers, important infrastructure, and industries from devastating earthquakes. Earthquakes are not predictable, but the seismic waves of an earthquake need some time to travel through the earth. You can have up to 30 seconds or even a minute to close gas pipelines, stop trains, and even inform people in affected areas. This can make a big difference.
editor: Thilo Kunzemann
publishing date: April 7, 2009
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