Japan's Meteorological Agency is using a new system on a trial basis that identifies a massive earthquake in a short time based on long-period ground motion.

The agency's system uses long-period tremors to determine whether a quake has a magnitude of 8 or higher within 3 minutes.

The system monitors long-period ground motion lasting from 100 to 500 seconds, which is specific to massive quakes.

The agency must issue a warning within about 3 minutes of an earthquake to prepare for its impact and tsunami, but the scale of a massive earthquake cannot be calculated accurately in a short time.

In the wake of the March 11th earthquake last year, the agency initially estimated its magnitude at 7.9, when it was actually magnitude 9.0. The ensuing tsunami was predicted to be much lower than it really was.

The new system is able to identify the size of a quake by comparing its jolts with those recorded in a magnitude-8 earthquake that hit off Hokkaido in 2003.

The agency will confirm the accuracy of the system during the trial period and start using it for issuing warnings in April.

News  credit: http://www3.nhk.or.jp/daily/english/20120212_15.html

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