No California Tsunami Warning After Big Quake in Alaskan Islands

Update, 3:55 p.m. Monday: The West Coast-Alaska Tsunami Warning Center has downgraded an alert issued in the wake of an 8.0-magnitude earthquake in the Aleutian Islands early Monday afternoon.

The center's latest advisory is forecasting a minor tsunami, with a maximum wave height of about a foot, along a 900-mile swath of remote islands from Attu in the west to Unimak in the east. For the rest of the West Coast, the advisory is for information only — meaning no threat is forecast. The Pacific Tsunami Warning Center in Honolulu said earlier this afternoon that the quake, which struck at 1:53 p.m. PDT near Little Sitkin Island, did not pose a threat to Hawaii. Little Sitkin Island, an unpopulated island dominated by an active volcano, is about 1,300 miles southwest of Anchorage and 3,000 miles northwest of San Francisco.

Original post: Federal tsunami forecasters are sizing up a possible threat to the West Coast after an 8.0 earthquake struck Alaska's Aleutian Islands early Monday afternoon.

The U.S. Geological Survey says the quake occurred at 1:53 p.m. PDT and was centered near Little Sitkin Island, near the southwestern end of the Aleutians. The USGS puts the depth of the quake at about 70 miles beneath the surface.

The West Coast-Alaska Tsunami Warning Center issued alerts for the islands closest to the epicenter and said it's assessing the threat to the West Coast. Little Sitkin Island is about 3,000 miles northwest of San Francisco.

"Right now it's looking like the impact is going to be confined mostly to the islands," said Scott Langley, a forecaster with the warning center in Palmer, Alaska. "We have been seeing water moving at Amchitka and Adak."

Amchitka is an unpopulated island, formerly home to a U.S. military bases and site of Cold War nuclear tests, about 20 miles southeast of Little Sitkin. Adak, about 200 miles to the east, has about 300 residents.

Langley said the impact on the U.S. and Canadian West Coast was still being evaluated. "It's a rapidly evolving situation," he said.

In Honolulu, the Pacific Tsunami Warning Center declared the earthquake's epicenter was too deep to pose a threat to Hawaii or most of the Pacific Basin.

Many coastal points along the California coast, notably Santa Cruz and Crescent City, suffered significant tsunami damage after a 9.0-magnitude earthquake struck northeastern Japan in March 2011.

Here's an excerpt from the latest bulletin from the West Coast-Alaska Tsunami Warning Center, which, again, says it's still assessing the potential impact on the West Coast:

TSUNAMI WARNING IN EFFECT FOR...

* THE COASTAL AREAS OF ALASKA FROM NIKOLSKI ALASKA TO ATTU
ALASKA

TSUNAMI ADVISORY IN EFFECT FOR...

* THE COASTAL AREAS OF ALASKA FROM UNIMAK PASS ALASKA /WHICH
IS LOCATED 80 MILES NE OF UNALASKA/ TO NIKOLSKI ALASKA

* FOR OTHER US AND CANADIAN PACIFIC COASTS IN NORTH AMERICA -
THE LEVEL OF TSUNAMI DANGER IS BEING EVALUATED. FURTHER
INFORMATION WILL BE PROVIDED IN SUPPLEMENTARY MESSAGES.

IMPACTS FOR TSUNAMI WARNING AREAS
---------------------------------
* WIDESPREAD DANGEROUS COASTAL FLOODING ACCOMPANIED BY POWERFUL
CURRENTS ARE POSSIBLE AND MAY CONTINUE FOR MANY HOURS AFTER
TSUNAMI ARRIVAL.

* THE FIRST WAVE MAY NOT BE THE LARGEST.

IMPACTS FOR TSUNAMI ADVISORY AREAS
----------------------------------
* A TSUNAMI CAPABLE OF PRODUCING STRONG CURRENTS OR WAVES DANGEROUS
TO PERSONS IN OR VERY NEAR THE WATER IS EXPECTED.

* CURRENTS MAY BE HAZARDOUS TO SWIMMERS... BOATS... AND COASTAL
STRUCTURES AND MAY CONTINUE FOR MANY HOURS AFTER THE TSUNAMI
ARRIVAL.

* THE FIRST WAVE MAY NOT BE THE LARGEST.