A man climbs up a collapsed house following the magnitude 6.9 earthquake which killed 1 person and injured at least 214, on March 25. AP PHOTO

The system detects the first underground tremors arriving before the main quake and estimates their intensity before big seismic waves reach the surface.

"That's why we could issue the alert in a minute," said Yosuke Igarashi,official at the Meteorological Agency.

"We started operation of the early-warning system last year, but until now there was no opportunity to use it to issue a tsunami warning," he said.

Before the new system was introduced it usually took the agency about three minutes to issue a tsunami alert after a major quake.

The early-warning system for tsunami alerts was introduced in October, officials said.

Aftershocks continued to hit the Hokuriku region after March 25. The powerful earthquake killed one person and injured at least 214 in Ishikawa, Toyama and Niigata prefectures.

The Japan Times Weekly: March 31, 2007
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