On shaky ground
Feb 27, 2012 1 comment
A spate of recent earthquakes, including major events in Japan, New Zealand and Haiti, has reminded us of the sheer devastation that can be wrought by the Earth's tectonic plates. But what is also shocking about earthquakes is that they are so difficult to foresee. So why is it so difficult to predict when and where the next major quake will strike? This short film explores this question and looks at the efforts that are being made to develop systems for earthquake forecasting.
The film presents an introduction to the key concepts in earthquake science, through a collection of interviews, explanations and animations. It opens with an account of how people have tried to look for signs that a major earthquake might be imminent. As David Schwartz, an earthquake geologist with the US Geological Survey, points out, "There was radon-gas emission, and that didn't work. There was animal behaviour, and that didn't work. And in reality it's really hard to find something that's easily definable like that."
But seismologists have not given up hope of predicting earthquakes. The film also looks at attempts to identify geographical regions that may be at risk. This is an area of interest to Aldo Zollo, a geophysicist at the University of Naples, Federico II in Italy, whose own career in seismology was triggered by an earthquake. Zollo recounts the day in 1980 when, as a physics student living in the Apennines, he returned home one day to find his house damaged by an earthquake.
Zollo describes his efforts and those of others around the world to develop "earthquake forecasts", which place probabilities on the likelihood of earthquakes occurring. It works, he explains, by studying the distribution and timing of earthquakes within a defined region. "It helps local administrators, scientists and civil-protection managers to deal with their preparedness for earthquakes, and to educate people to be prepared for the next earthquake," he says.
Another scientist in the film with an interest in forecasting earthquakes is Donald Turcotte, of the University of California, Davis, in the US. Turcotte takes a mathematical approach, which asserts that the magnitude and distribution of earthquakes obey the distinct "scaling laws" described by fractals. "In general, you can expect that where you have 10 magnitude-five earthquakes in a period of time, you expect to have one magnitude six," he says. "We have used this to establish a risk basis globally."
Turcotte concedes, however, that the underlying physics behind this distribution is still not fully understood. And, tellingly, that the approach could not have been used to forecast the Japanese earthquake of 2011 because it still deals in generalities. In other words, there are still great uncertainties when trying to predict specific earthquake events.
The film concludes with a look to the future and the possibility of using the Global Positioning System (GPS) to closely monitor fault zones. David Schwartz introduces the idea of studying the changing strain in rocks in real time to identify particular locales where a slip could be about to occur. "There may be a time when you can turn on your TV at night and in addition to getting the weather report, you'll get the strain report," speculates Schwartz. "And maybe that'll be a way to say 'Hey look, let's keep our eye on Seattle Washington because it looks like something might be building up'."
All the interviews were filmed in San Francisco at the 2011 Fall Meeting of the American Geophysical Union.
About the author
James Dacey is multimedia projects editor for Physics World