US Geological Survey, Pasadena, California

A seismologist considers a new method of earthquake prediction.

I am acutely aware that numerous methods of earthquake prediction at one time held great promise, but fell apart under proper scrutiny. In recent years, I have heard about many studies purporting to uncover evidence of electromagnetic precursors, almost all of which involved weak or non-existent statistical analysis.

But occasionally I come across research that is not so easy to dismiss. For example, data from the French micro-satellite DEMETER, which was launched in 2003 to investigate electromagnetic perturbations in the ionosphere, have been analysed by a team of French and Czech researchers (F. Nmec et al. Geophys. Res. Lett. doi:10.1029/2007GRL032517; 2008). These authors find that there are very-low-frequency electromagnetic fluctuations in the ionosphere above the epicentres of moderate and large earthquakes that occur a day or two before the ground starts to shake.

Nmec and colleagues’ results could be fatally flawed. If electromagnetic disturbances are generated when earthquakes occur, what are apparently true signals of one earthquake could actually be signals related to a preceding shock. Or the analysis might go awry because of subtle data-selection biases. But if there are fatal flaws, they are not obvious.

In any case, as the authors themselves emphasize, the significance of the DEMETER results can be demonstrated only when data from many earthquakes are averaged. This highlights a key point: it is entirely possible for precursors to be real but of no use for prediction. If earthquake scientists can separate consideration of earthquake precursors from the highly charged debates about earthquake prediction, the research community might just learn something about earthquake processes.

US Geological Survey, Pasadena, California

A seismologist considers a new method of earthquake prediction.

I am acutely aware that numerous methods of earthquake prediction at one time held great promise, but fell apart under proper scrutiny. In recent years, I have heard about many studies purporting to uncover evidence of electromagnetic precursors, almost all of which involved weak or non-existent statistical analysis.

But occasionally I come across research that is not so easy to dismiss. For example, data from the French micro-satellite DEMETER, which was launched in 2003 to investigate electromagnetic perturbations in the ionosphere, have been analysed by a team of French and Czech researchers (F. Nmec et al. Geophys. Res. Lett. doi:10.1029/2007GRL032517; 2008). These authors find that there are very-low-frequency electromagnetic fluctuations in the ionosphere above the epicentres of moderate and large earthquakes that occur a day or two before the ground starts to shake.

Nmec and colleagues’ results could be fatally flawed. If electromagnetic disturbances are generated when earthquakes occur, what are apparently true signals of one earthquake could actually be signals related to a preceding shock. Or the analysis might go awry because of subtle data-selection biases. But if there are fatal flaws, they are not obvious.

In any case, as the authors themselves emphasize, the significance of the DEMETER results can be demonstrated only when data from many earthquakes are averaged. This highlights a key point: it is entirely possible for precursors to be real but of no use for prediction. If earthquake scientists can separate consideration of earthquake precursors from the highly charged debates about earthquake prediction, the research community might just learn something about earthquake processes.