Earthquake [earthquake warning systems]

Accurate earthquake warnings are, at last, within reach. Instead of coming from the mechanical phenomena that have been the focus of decades of study, however, they will come from electromagnetic phenomena. And, remarkably, these predictions will come from signals gathered not only at the earth's surface but also in the ionosphere. It has been observed that electromagnetic disturbances happen during the days that precede an earthquake. These disturbances happen when crystalline rocks are deformed by the slow grinding of the earth that occurs just before an earthquake. The cracking creates tremendous electric currents in the ground, which travel to the surface and into the air. These currents alter the magnetic field surrounding the earthquake zone and these electromagnetic effects can easily be detected. While such an earthquake warning system would be useful, there are a number of technical and financial problems that need first to be addressed before they can be installed worldwide.