[alikim]

I've actually done this and get notifications usually 30 seconds post quake just like xkcd suggested.

[dheera]

I thought of that but 30 seconds is too long for an early warning system, the waves travel pretty fast.

[alikim]

Depending on where the epicenter is, it may take 1-2 minutes for the S waves (which are the slower, damaging ones) to travel to the major population center. Up to 30s of warning for an earthquake early warning system is enough for people to take cover and for cities to shut off things like water/gas lines. That being said my system is definitely not ready for that, and twitter can be seen as one source of information used to augment other early detection systems.

[dragonwriter]

The only way to get notification of an earhquake in time is a prediction system.