From: terwill@arecibo.aero.org (Bill who?)
Subject: Re: Tornadoes ???
News-Software: VAX/VMS VNEWS 1.41    
Reply-To: terwill@arecibo.aero.org
Organization: The Aerospace Corporation
Date: Thu, 27 Aug 1992 21:11:00 GMT

> 
>There was a threat of a tidal wave in the late sixties (saw it on
>Dragnet). Didn't come to much when it got here. Tsunamis are
>generated by undersea earthquakes. We're just lucky about the
>placement of the really nasty faults in the Pacific.
> 
>-dh


When the Good Friday (March 27, 1964, 5:36pm Alaska time) earthquake hit Prince
Williams Sound in Alaska (originally an 8.4 on the R scale, upgraded to a 9.2
after analysis of the data, shaking lasted for 4.5 minutes, yes minutes, and
the first shock was a 7-15 foot drop of the entire plate which included the
city of Anchorage!) fear of a possible tsunami along the entire west coast of
the lower 48 was suddenly a reality and there was a minor local panic. The
resulting tidal wave did kill 16 people along the Oregon and Northern
California coast but never made it this far south. I remember I was in grade
school, lived in Reseda and was worried that "the Big Wave" was coming! 

In Anchorage, and the Kenai Pennisula which extends south and west from
Anchorage, the normal tidal displacement (difference in low and high tide) is
33 feet. (somewhere in northeast Canada it is in excess of 50 feet!) This may 
have helped Anchorage as it was low tide and the Turnagain and Knik Arms
of Cooks Inlet that the city is 2/3 surrounded by were empty and could absorb
a lot of the generated wave. 

And the constant shaking of a 9.2 magnitude quake for 4.5 minutes (when it
shakes for more than 15 seconds here in LA you think it is a lifetime!) just
puts out wave after wave which tend to "stack up" as they radiate out from the
epicenter of the earthquake. As such, wave activity close to the quake's center
may not look like much, although the fishing town of Seward on the Kenai
pennisula facing the epicenter was destroyed by the tital wave
with 13 people killed and Kodiak, south and west of the epicenter on Kodiak
Island was also destroyed with 6 fatalities. But if a tsunami can travel for 
several hundred miles uninterrupted, like it did to the Oregon/ Northern
California coast, well, they can be very serious, especially to populated
coastal areas, something Alaska still does not have :)

One other point of interest about this quake: there was a noticible abrupt 
change in the levels of well water felt as far away as South Africa! This
would indicate that the shock didn't simply pass from plate to plate but
through the earths core. Interesting. Yes, there has been a bigger quake
recorded, in Chili in 1968, 9.5 in a very remote mountain region south
of the 45th parallel. This quake was said to have, according to indiginous
tribes in the area, actually changed the horizon and leveled mountains.
Kind of a bibilical thing. The shock in Argentina, on the other side of
the Patagonias (a large serious granite mountain range) killed several
people in remote locations there!

Not to worry, when the big one hits everything east of the San Andreas
fault will fall into the Atlantic Ocean :)

Bill
Newsgroups: la.general