With the aftermath of the devastating earthquake in Pakistan still in the headlines, our cover story this month, "Earthquake Alarm", takes on added relevance. Authors Tom Bleier, CEO of QuakeFinder, in Palo Alto, Calif., and Friedemann Freund, a senior researcher at NASA Ames Research Center, in Mountain View, Calif., consider the possibility that we may soon be able to predict where and when earthquakes will occur, enabling potential victims to take precautions.
"It seems that earthquakes should be predictable," write Bleier and Freund. "After all, we can predict hurricanes and floods using detailed satellite imagery and sophisticated computer models. Using advanced Doppler radar, we can even tell minutes ahead of time that a tornado will form."
So, why not earthquakes? The authors say that such short-term forecasts are within reach.
"They will come not from the mechanical phenomena—measurements of the movement of the earth's crust—that have been the focus of decades of study, but, rather, from electromagnetic phenomena. And, remarkably, these predictions will come from signals gathered not only at the earth's surface but also far above it, in the ionosphere."
The tell-tale signs of an impending earthquake have been noted for years by scientists, after the fact; it is only recently that technology is being put in place to take advantage of these signals in advance of a temblor.
One of the signs is a light or glow in the sky—white, blue, or orange in color, extending some hundreds of meters in the air and spreading for several kilometers across the ground. Another is a disturbance in the ultralow frequency radio band noticed in the weeks and more dramatically in the hours prior to an earthquake.
"Both the lights and the radio waves appear to be electromagnetic disturbances that happen when crystalline rocks are deformed—or even broken—by the slow grinding of the earth that occurs just before the dramatic slip that is an earthquake," the authors explain. "Although a rock in its normal state is, of course, an insulator, this cracking creates tremendous electric currents in the ground, which travel to the surface and into the air."
Soon, forecasters could use ground-based sensors and satellites "to detect all these precursor signals—electronically detected ELF and ULF magnetic-field changes, ionospheric changes, infrared luminescence, and air-conductivity changes—along with traditional mechanical and GPS monitoring of movements of the earth's crust."
"Forecasters may then be able to issue graduated warnings within weeks, days, and hours, declaring increasing threat levels as the evidence from different sensors begins pointing in the same direction."
Bleier and Freund believe we are only about ten years away from implementing a system that officials and the public will come to trust. "Then governments in active earthquake areas such as California, China, Japan, Russia, and Taiwan could install warning systems as early as 2015, saving lives and minimizing the chaos of earthquakes."
That will be a major boon to humankind.