Major South Pacific Quake Spawns Tsunami
By LiveScience Staff
posted: 29 September 2009 03:20 pm ET
Updated 6:01 p.m. ET:
Editor’s Note: The Pacific Tsunami Warning Center cancelled all warnings and watches associated with this event. The article below remains as last updated prior to the cancellations.
A major earthquake struck in the Somoa Islands region of the South Pacific Ocean. The preliminary magnitude was 7.9, according to the USGS, which later upgraded the temblor to 8.0.
A tsunami warning was issued for New Zealand and nearby islands but it’s not yet clear if any real danger exists.
AP reports that a tsunami rolled 100 yards inland at Pago Pago in American Samoa, but few details were provided. Reuters reports there are deaths, citing a U.S. National Park Service official. Various wave heights are being reported, from 5 feet to 20 feet high.
Even major earthquakes under the sea do not always generate significant tsunamis. It depends on whether and how much the floor of the sea shifts. A tsunami can be created when a significant thrust on the seafloor acts like a giant paddle.
No tsunami is expected along the California, Oregon, Washington, British Columbia, and Alaska coasts, the Pacific Tsunami Warning Center said initially. The center did, however, release a map showing how long it would take for any possible tsunami from this quake to reach various shorelines in the Pacific basin. A tsunami watch — not a warning — is now in effect for Hawaii. Tsunamis can take hours to cross the open ocean.
This quake was centered 1,670 miles (2685 km) from Auckland, New Zealand and just 125 miles from one of the Samoan islands. It originated 21.7 miles (35 km) beneach the seafloor. It struck at about 1:48 p.m. ET.
On the open ocean, a tsunami is barely noticeable. A wave that might be just inches high can soar to building-tall proportions as it meets a rising seafloor near the coast.
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