(Poster's Note: thought this was interesting enough to send it out to all quake related groups)
Japan's Cell Phones Vibrate to Warn of Earthquake
Published : Wednesday, 29 Sep 2010, 9:04 PM EDT
(NewsCore) - The success of a system that uses cell phones to warn people after an earthquake has occurred, before its tremors reach them, was being assessed by seismologists in Japan on Wednesday.
All over northern and central Japan, millions of people received a warning on their cell phones Tuesday that a strong earthquake had occurred in Fukushima Prefecture.
About 30 seconds later the tremors hit Tokyo -- giving businesses and individuals time to brace themselves for the impact.
In Tokyo subway trains halted in tunnels, and people telephoned loved ones and clambered under tables. The earthquake turned out to be relatively mild -- 5.8 on the Richter scale -- but with a maximum intensity of 4, meaning that it rattled houses but caused no serious damage.
It represented a success for a system that has suffered embarrassing failures.
The Earthquake Early Warning system began in 2007 and has cost the Japanese Government ¥1.7 billion (US$20.2 million) over the past ten years. It depends on the two sets of energy waves emitted by an earthquake. The secondary waves cause shaking and damage but are preceded by less powerful preliminary waves.
The early warning system consists of a set of nationwide sensors that detect the earlier preliminary waves and use them to transmit information about the strength and location of the earthquake to the Japan Meteorological Agency. From there a warning is sent to television and radio stations and cell phones.
People closest to the epicenter will have little or no time to react, but those farther away will see the warning a few tens of seconds before the earthquake reaches them.
It is intended to allow trains to be stopped, motorists to pull over and factories to secure objects. Doctors performing surgical procedures and steeplejacks are other beneficiaries, as well as the public, who are given an opportunity to take shelter under tables and doorways.
The system has not always worked well. Police have been on the trail of fraudsters who have sold earthquake warning devices on the assurance that they were compulsory under the law, and made exaggerated claims for their effectiveness.
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