Friday, May 2, 2008

Alaska quake: no tsunami threat, but a caution

A powerful earthquake Thursday afternoon in the Andreanof Islands of Alaska's Aleutian chain did not launch a tsunami toward Hawai'i, but it's a clear warning.

Two of the most damaging tsunami in Hawai'i history came from the same region.
(Image: Pacific Tsunami Warning Center chart of the recent Alaska temblors.)
The Pacific Tsunami Warning Center report of no tsunami hazard went out at 3:46 p.m. Hawai'i time, just 12 minutes after the 3:34 p.m. shake, which registered a 7.0, although later recalculations dropped it to magnitude 6.6.
“A destructive Pacific-wide tsunami is not expected and there is no tsunami threat to Hawai'i,” said a statement from the center.
The quake was centered at 51.8 degrees north and 177.6 west. That placed it a little more than 1,200 miles from Anchorage.
“It was a pretty good-sized quake. It was heavily felt in the Adak area,” said Bruce Turner, geophysicist and science officer with the West Coast and Alaska Tsunami Warning Center.
It normally takes a considerably larger quake to generate a significant tsunami, but it was interesting that Alaska had a very active day Thursday from an earthquake perspective. (see
Just a day earlier, at nearly the same location, there was a 5.1 quake. And smaller shakers have rumbled up and down the Aleutian chain during the past 24 hours, most of them located in the immediate vicinity of these earthquakes.
The 1946 tsunami that caused severe damage in Hawai'i came from a location at 52.8 degrees north and 163.5 degrees west, about 900 miles away.
The 1957 tsunami came from a quake quite close to yesterday's temblor. It was at 51.5 degrees north, 175.7 degrees west, just 84 miles away and within the Andreanof Islands.
Thanks to an advanced Pacific tsunami warning system, Hawai'i residents are likely to get several hours of notice of the arrival of a tsunami generated from the Alaskan region—plenty of time to update their evacuation kits and get away from the coast.
Locally generated tsunami are a different story. There may be only minutes. And if you're on the island where the wave was generated, you need to move to high ground as soon as you feel the ground shaking.
From a statistical standpoint, Hawai'i has been free of damaging tsunami for an unusually long time. Does it mean one is imminent? Not necessarily, but it pays to be ready.
One ready place to look for information is the phone book. The directories once had the emergency information section reliably in the front pages, but some now have those pages in the middle section of the book.
These pages include tsunami inundation maps. If you live within a few blocks of the shore, check the map to see whether you are in an evacuation area.
Most residents should have an emergency evacuation kit at hand. It will include your prescription medications, glasses, cash and special items like special foods, diapers for babies and important personal documents. It might also include a personal first aid kit, water, flashlight and other gear. A more complete list is in the phone book.
Here are other earthquake resources:
Earthquakes Data Magnitude 5.0 and Over 2005 - 2014
In addition you can find more info on the topic below:
Seismic Monitor
Quakes - Live Earthquakes Map

© 2008 Jan W. TenBruggencate