Japan's false alarm showcases tsunami alert system

A powerful undersea earthquake prompted tsunami warnings Wednesday for Japan, Russia, and Alaska, but it was a false alarm. Only a series of tiny waves hit the northern Japanese coast.

Still, the event served as a useful test of Japan's sophisticated early warning system and of its civil defense emergency procedures designed to speedily remove people from low-lying coastal areas.

Japan issued a major tsunami alert for the northern coast of Hokkaido and some parts of northern Honshu Wednesday evening local time, sparking the evacuation of hundreds of thousands of people in some of the most remote and inaccessible parts of the nation.

The emergency began after a magnitude-8.1 earthquake struck in the Kuril Islands some 110 miles northeast of Hokkaido. The area where the earthquake occurred has seen temblors over a magnitude of 8.0 occurring in 1994 and 2003.

"The region has been particularly active since September," says Takeshi Hachimine, director of the earthquake and tsunami warning system section at the Japan Meteorological Agency (JMA).

Still, Japan is perhaps the best-prepared country in the world for these events. It boasts an extensive system of more than 300 round-the-clock earthquake sensors distributed in the waters surrounding the island nation that relay real-time information to six regional centers. The system has a reputation for being able to predict within five minutes of a quake's occurrence whether a tsunami will strike.

The JMA issued the alert some 14 minutes after the temblor, much slower than is typical for the many minor tsunami warnings that periodically occur in the country. Still, that was enough time for most of the small towns along the bleak Sea of Okhotsk coast to usher people to safety.

The town of Sarufutsu, for example, was able to get its entire population of 2,904 people to higher ground within one hour.

Tsunami escape routes and towers were built along most populated parts of the Hokkaido coast after waves of up to 30 meters tall devastated the town of Okushiri there in 1993. The Okushiri tsunami was caused by a quake that was so close to land that there was virtually no time for residents to flee, and 202 perished in the waters.

That disaster prompted Japan to improve its early warning system and set up comprehensive evacuation plans for coastal towns. The government has since periodically commissioned studies into the probable effects of a major tsunami on populated coastal areas in order to devise steps to mitigate the damage. One such study conducted in 2003, showing that a tsunami resulting from magnitude-8.6 quake in the Pacific south of Japan could kill up to 8,600 people if evacuations were slow, prompted local municipalities to improve escape routes. Other methods introduced to minimize damage include giant water gates that can be closed to prevent killer waves from heading inland via river systems

Japan got off lightly this time around. The waves did not swell higher than 16 inches. Some three hours after the initial tsunami alert was sounded, the JMA reduced the emergency level for the northern coast of Hokkaido to a less serious "tsunami advisory."

A tsunami warning posted for coastal areas of Alaska was later canceled, as were watches for Hawaii and the northern tip of British Columbia and precautionary advisories for the states of Washington, Oregon, and California.

• Material from wire services was used in this story.