March 25, 2011
The p-wave network
Japan is blanked by p-wave detectors. During an earthquake, the primary (pressure) waves propagate faster than the destructive secondary (shearing) s-waves. Depending on the distance from the fault, the lead time can be up to a minute. This early warning system stops Shinkansen trains and scrams nuclear reactors.
All of the reactors at Fukushima scrammed during the Sendai earthquake. It was the latent heat that caused all the problems when the backup generators powering the cooling system were wiped out by the tsunami. A nuclear reactor is basically a big stove, and it stays hot for a long time after the power is turned off.
Japan's earthquake detector network functions like Watches/Warnings alerts from the National Weather Service. When the triggering threshold is reached, a graphic pops up on your television screen, identifying the location of the quake. A few minutes later, a graphic or text scroll lists the magnitude and the affected areas.
There's a cell phone app for that too. And Yahoo Japan (and other sites, I'm sure) pops up a banner with similar information. The television graphic is accompanied by this sound. The first couple of days after the Sendai earthquake, it happened so often I started to feel like one of Pavlov's dogs.
Sendai earthquake (1)
Sendai earthquake (2)
Sendai earthquake (3)