Hi redflare,
If your interested you may want to have a look at
http://www.meteoquake.org/researcha.htmlWhat is quite interesting is that there appears to be way of predicting earthquakes from a few days to a few hours before hand which has a statistical correlation.
It could be that a combination of the analysis of using the GPS system data to produce live dynamic ionospheric electron density mapping measurements and infra-red imagery from MODIS and NOAA satellites could be a statistically viable way of predicting large to medium sized earthquake events a few days to a few hours prior to the event.
If this is the case then I suspect that an earthquake warning system is already in place and that the authorities would have this information as construction of this earthquake warning system would merely be a specialised computer program.
The problem of course would be, would the authorities give warnings to the public. For example would the government issue an earthquake warning stating for example there would be a 65% chance of a localised earthquake in the San Fransico bay area in the next 48 to 72 hours with a predicted 6.5-7 magnitude? Would they sit on this info or would they warn the public dispite the consequences?
In China they already have a public earthquake anouncement system.