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Web Extra Wednesday, November 15, 2006 updated Nov. 16, 10:30 a.m. EST

Earthquakes, tsunamis strike Japan

A magnitude-8.3 earthquake struck off the Kuril Islands between Japan and Russia Wednesday at 10:14 p.m. local time, followed by a series of strong aftershocks, at least four of which were above magnitude 6.0, according to the U.S. Geological Survey (USGS). USGS initially put the earthquake's magnitude at 7.8; the Japan Meteorological Agency initially measured the earthquake's magnitude at 8.1.

The Japanese agency immediately issued tsunami warnings for Russia and Japan, where several small tsunami waves have since washed ashore, ranging from a few centimeters to 40 centimeters in height. The agency initially warned that tsunami waves up to 2 meters high could strike much of Japan's coastline, but withdrew the warning several hours later.

The Pacific Tsunami Warning Center in Hawaii issued tsunami warnings for Guam, Midway Island, Taiwan and other islands in the Pacific Ocean, and issued a tsunami watch for Hawaii. The center suggested that if tsunami waves were to hit Hawaii, the arrival time would have been 7:20 a.m. local time. No tsunami was observed, however, and the watches and warnings for the region were canceled.

Likewise, the West Coast and Alaska Tsunami Warning Center in Alaska issued tsunami warnings for Alaskan coastal areas, with watches being issued for Washington state and British Columbia, and precautionary advisories for Oregon and California. If tsunami waves were to arrive on the coasts of Canada and the United States, wave heights would not be expected to exceed a few centimeters and thus not to be a danger to anyone outside of the waterfronts in these areas, the center wrote in their tsunami bulletin issued Wednesday morning. By noon Eastern time, the center canceled all warnings and watches. Still, the center said that even small sea-level changes can be hazardous to boats and coastal structures, so people should take caution. As of Wednesday, no deaths were reported from the quake or tsunamis, according to USGS.

Today, however, the West Coast and Alaska Tsunami Warning Center reported that some locations in the United States did see increased wave heights following the earthquake. Kahului, Hawaii, saw a maximum height of 76 centimeters (30 inches), and Crescent City, Calif., saw a maximum wave height of 88 centimeters (35 inches). The surge, possibly associated with the earthquake, reportedly destroyed two docks in Crescent City and caused an estimated $700,000 of damage, according to a Nov. 16 Associated Press story.

Such damage pales in comparison to the $7.5 million worth of damage incurred by Crescent City after a tsunami struck land following the 1964 Good Friday earthquake in Alaska, according to USGS. That tsunami measured more than 20 feet tall at Crescent City, killing 11 people.

Wednesday's earthquake struck about 445 kilometers (275 miles) northeast of Kuril'sk, Kuril Islands, and 1,665 kilometers (1,030 miles) northeast of Tokyo, Japan, USGS reported. It occurred about 28 kilometers below the seafloor.

Undersea earthquakes and ensuing tsunami warnings have grabbed people's attention, following the devastating magnitude-9.1 earthquake and tsunami off Sumatra in 2004 that killed more than 200,000 people around the Indian Ocean.

Japan experiences more earthquakes than most parts of the world, as the country sits atop four converging tectonic plates. It is also part of the so-called Ring of Fire, a tectonically and volcanologically active area that rims the Pacific Ocean.

Megan Sever

Links:
"Guarding Against Tsunamis: What Does it Mean to be Ready?" Geotimes, November 2006

Japan Meteorological Agency tsunami warning
U.S. Geological Survey Earthquake Hazards
Pacific Tsunami Warning Center
West Coast and Alaska Tsunami Warning Center
News story by Associated Press, Nov. 15, 2006
News story by Associated Press, Nov. 16, 2006

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