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Magnitude 8.0 earthquake in southern Pacific triggers tsunami, warnings
Published: 02/05/2013 17:51:30
Updated: 02/05/2013 19:30:40

Estimated maxium height for tsunami caused by 8.0 earthquake in southern Pacific on February 5, 2013
Estimated maxium height for tsunami caused by 8.0 earthquake in southern Pacific on February 5, 2013 (European Union JRC / GDACS.org)

Estimated travel & arrvial times for tsunami caused by 8.0 earthquake in southern Pacific on February 5th 2013
Estimated travel & arrvial times for tsunami caused by 8.0 earthquake in southern Pacific on February 5th 2013 (WCATWC / KATH-TV)

Related:
Earthquake and tsunami readiness depends on information and planning

A magnitude 8.0 earthquake near the Santa Cruz Islands in the southern Pacific ocean at 4:12 PM Alaska time on Tuesday triggered a tsunami and expanding warnings in the region. Tsunami warning centers in Alaska and Hawaii did not issue warnings for Hawaii or the mainland US, Canada or Alaskan coast after determining there was no threat from the tsunami for those areas.

Tsunamis generated by large earthquakes in certain areas of the earth's crust can travel across oceans and cause devastation thousands of miles away. The waves can travel at hundreds of miles an hour in deep water, slowing down and growing in height when they reach land. Warnings for areas close to an earthquake are generally issued automatically based on initial data. Warnings for areas further from an earthquake's epicenter are normally only issued after forecasters have had time to include sea level sensor data in updated models and at risk areas have been identified. The delay for improved manual forecasting minimizes unnecessary warnings while still providing for enough time for an alert before waves arrive, should one be necessary.

Initial models forecast that the earliest a possible wave would reach Hawaii was around 10 PM Hawaii time Tuesday. A possible tsunami would reach the west coast of the US and Canada, including Alaska in the early hours of Wednesday morning. Tsunami travel times are automatically calculated by computer and do not provide any indication of the size or energy of a wave; only the time it would take a possible wave to travel across the ocean to provide an indication of how long there is to forecast a warning and prepare for any threat should one be deemed likely.

In a statement at 4:49 PM Alaska time the Pacific Tsunami Warning Center said that a 3 foot wave had been measured at an island near the epicenter. Hawaii was never placed under warning, and at 5:30 PM Alaska time stated there was no danger to Hawaii: "BASED ON ALL AVAILABLE DATA A DESTRUCTIVE PACIFIC-WIDE TSUNAMI IS NOT EXPECTED AND THERE IS NO TSUNAMI THREAT TO HAWAII. REPEAT. A DESTRUCTIVE PACIFIC-WIDE TSUNAMI IS NOT EXPECTED AND THERE IS NO TSUNAMI THREAT TO HAWAII. - A TSUNAMI HAS BEEN CONFIRMED IN AREAS NEAR THE EPICENTER BUT IT SHOULD NOT AFFECT HAWAII."

At 6:22 PM Alaska time the West Coast & Alaska Tsunami Warning center issued a statement saying there was no danger to North America: "Evaluation: * No tsunami threat exists for the U.S. west coast, British Columbia, or Alaska. * Some of the areas listed above may experience non-damaging sea level changes. * Sea level observations indicate a tsunami was generated."

The United Nations' Global Disaster Alerts and Coordination System reported tsunami waves as high as 2.0 meters (6.6 feet) impacting parts of the Solomon Islands.

The Pacific Tsunami Warning Center cancelled warnings for the southern Pacific region at 6:47 PM Alaska time and reported the following tsunami observations:

 GAUGE LOCATION        LAT   LON    TIME        AMPL         PER

------------------- ----- ------ ----- --------------- -----
LUGANVILLE VU 15.5S 167.2E 0319Z 0.26M / 0.8FT 28MIN
DART 55023 14.8S 153.6E 0326Z 0.05M / 0.2FT 06MIN
HIENGHENE NEW CALED 20.7S 164.9E 0319Z 0.55M / 1.8FT 14MIN
LIFOU NEW CALEDONIA 20.9S 167.3E 0309Z 0.48M / 1.6FT 10MIN
VANUATU 17.8S 168.3E 0255Z 0.15M / 0.5FT 16MIN
DART 52406 5.3S 165.1E 0206Z 0.04M / 0.1FT 10MIN
DART 55012 15.8S 158.5E 0237Z 0.17M / 0.6FT 06MIN
LATA WHARF SB 10.7S 165.8E 0129Z 0.91M / 3.0FT 18MIN


SEA LEVEL READINGS INDICATE A TSUNAMI WAS GENERATED. IT MAY HAVE
BEEN DESTRUCTIVE ALONG COASTS NEAR THE EARTHQUAKE EPICENTER. FOR
THOSE AREAS - WHEN NO MAJOR WAVES ARE OBSERVED FOR TWO HOURS
AFTER THE ESTIMATED TIME OF ARRIVAL OR DAMAGING WAVES HAVE NOT
OCCURRED FOR AT LEAST TWO HOURS THEN LOCAL AUTHORITIES CAN ASSUME
THE THREAT IS PASSED. DANGER TO BOATS AND COASTAL STRUCTURES CAN
CONTINUE FOR SEVERAL HOURS DUE TO RAPID CURRENTS. AS LOCAL
CONDITIONS CAN CAUSE A WIDE VARIATION IN TSUNAMI WAVE ACTION THE
ALL CLEAR DETERMINATION MUST BE MADE BY LOCAL AUTHORITIES.

NO TSUNAMI THREAT EXISTS FOR OTHER COASTAL AREAS ALTHOUGH SOME
MAY EXPERIENCE SMALL SEA LEVEL CHANGES. FOR ALL AREAS COVERED BY
THIS CENTER...THE TSUNAMI WARNING AND WATCH ARE CANCELLED.

http://wcatwc.arh.noaa.gov/

By: Mikko Wilson - mikko@kath.tv