An Early Warning System For Earthquakes

Iphtashu Fitz writes "Would 15 seconds be enough warning time to prepare for an earthquake? It certainly wouldn't be long enough to evacuate from where you live, but it may be just long enough to get out of a building or brace yourself in a doorframe or under a solid desk. Italian scientists may have discovered a way to measure the initial shockwave of an earthquake two seconds after it starts, and from it predict the extent of the destructive secondary wave that will follow. It typically takes twenty seconds for the secondary wave to spread 40 miles, so sensors that can transmit warnings at the speed of light may provide just enough warning before a major quake for people to brace themselves. Even more importantly, such a warning could allow for utilities like gas companies to close safety valves, preventing potential fires or explosions in the aftermath of the quake."

Comments

One powerful earthquake?

[solafide]

It takes 20 seconds for it to travel 40 miles? How much power has that secondary wave lost in those 40 miles? Wouldn't it take one really powerful earthquake for you to need to take cover 40 miles from the epicenter?

(I'm not an expert on earthquakes, but 40 miles seems like a long way for the earthquake to travel.)

Re:One powerful earthquake?

[Beryllium Sphere(tm)]

1985, Mexico City, buildings collapsed when the center of the earthquake was 400 km away. That one was unusual but it shows what's possible.

The other thing you can do with 10-20 seconds of warning is apply emergency brakes on the bullet trains, which I believe Japan has arranged to do.

Safety valves?

[EaglemanBSA]

There would still be gas in the main lines, how would shutting a safety valve keep a broken pipe from leaking gas already in it?