[prothid]

A few seconds could shut down reactors, gas lines, slow trains, trigger stop-lights (e.g. preceding tunnels), alarm people in parking decks, etc.

Earthquakes are known to sometimes be preceded by unexplained balls of light much further in advance. If this phenomenon is related, the warning period likely exceeds just a few seconds.

[jofer]

Actually, there's a few seconds (depending on distance from the epicenter) warning already. Body waves ("P" and "S" waves) travel through the earth at a greater speed than surface waves (which are what actually cause damage).

Japan's high-speed rail lines are already programmed to shut down when a significant earthquake is (automatically) detected from body-wave arrivals.

Of course, this only helps if you're not very close to the epicenter of the earthquake.

Also, not to be too pedantic, but "earthquake lightning" has only been reliably documented after or during earthquake rupture. It is a weird and apparently real phenomenon, though.