The BBC have an interesting story that NASA have observed
sufficient correlation between disturbances in the ionosphere and earthquakes to merit serious feasibility study into earthquake forecasts. If this stands up it could be a huge, life-saving breakthrough, and something to wave in the face of the "...but why spend the money on space rather than [x, y or z]?" brigade.
QUOTE
On a significant number of occasions, satellites have picked up disturbances in this part of the atmosphere 100-600km above areas that have later been hit by earthquakes. One of the most important of these is a fluctuation in the density of electrons and other electrically-charged particles in the ionosphere.