Why Experts Can't Predict A Quake
Updated: 5:23pm UK, Monday 22 October 2012
By Thomas Moore, Health Correspondent
Three days before the L'Aquila earthquake a colony of common toads 50 miles away seemed to sense danger.
Every breeding pair fled, mystifying researchers who had been studying the toads.
Perhaps it was gases seeping from the Earth's crust that alerted them. Or maybe it was a build-up of charged particles in the atmosphere.
The truth is that earthquake scientists can't even come close to the toad's predictive powers.
They know where earthquakes are likely to happen - the Earth's tectonic plates and fault zones are reasonably well mapped. But they don't know when.
The best they can currently do is estimate the probability of a future quake in a particular area by studying the frequency and magnitude of tremors in the past.
So, for example, the US Geological Survey calculates that there is 62% chance of a strong earthquake striking San Francisco in the next 30 years.
But they can't hazard a guess on the likelihood of it happening next year. Even that is too narrow a time-frame.
Seismologists are using increasingly sophisticated equipment to monitor the movement of rocks around fault lines in the hope of spotting pressure points.
Researchers in California are developing a system that could give "between a few seconds and tens of seconds" warning of an earthquake. But that's barely enough time to alert the public, let alone to take cover.
Other research teams are using satellites to study the upper atmosphere for electrical disturbances that might signal a quake.
They believe that when rocks compress they generate an electrical current between the Earth's crust and the atmosphere. But that work is still on-going.
So for now nature seems to do it better. Snakes, deep-sea fish, birds and some mammals have been reported to act strangely ahead of an earthquake.
If scientists could tune in to whatever animals can detect, they might finally be able to give an accurate warning of an imminent earthquake.