-
Tsunamis travel at velocities between five hundred and
nine hundred fifty kilometers per hour
(300 to 600 miles/ hour).
- The height of the wave
itself is usually less than a meter (3ft)in the open ocean,
and the
distance between wave crests can be anywhere from
one hundred to seven hundred kilometers (62 to 435 miles)
apart.
- Many times these waves move through the open ocean
without being noticed.
- When this wave front comes on shore,
however, it hits the shallow
continental shelf
coastal
water and piles up on itself, resulting in a huge wave.
- The crest of a tsunami along shore shows up as
a rapid rise in the level of the sea that is very choppy
at the top.
- At times the first warning of the approach of a tsunami
is the water on the beach withdrawing rapidly into the
ocean to exceptionally low levels.
- If you ever see this
when you are at the beach, RUN (toward land)!! Five to
thirty minutes later a
surge
of water will hit which
can extend hundreds of meters inland
until it runs out
of water or comes up against something big enough to
stop it.
- After this come more rapid retreats of the ocean,
with more surges to follow. These new surges can be from
ten to sixty minutes apart.(3)
Tsunami waves generated by this earthquake
came on shore along the Alaskan coast,
western coasts of both North and South America, Hawaii,
and Japan. It was the second largest tsunami ever recorded. In
Alaska, Chenega was completely destroyed and the port at
Seward demolished.(3) The first wave of the tsunami hit the
Kenai Peninsula in nineteen minutes and Kodiak Island in
thirty four minutes. It took four hours to hit the
northern California coast and Crescent City.(1)
The Crescent City Story
Crescent City is in California just south of the Oregon
border. It sustained eight million dollars worth of damage,
and eleven people died, yet no damage was reported to
either the immediate north or south of the city.
Why?
In general, a city built on flat land is more susceptible
to damage from a tsunami than one built on a steep cliff
because the
tsunami runup
, the height above sea level to which
the tsunami wave rises above land, must be greater than
the local topography. The
topography
of the sea floor outside of Crescent City
itself is such that it concentrated the wave energy onto
a narrow stretch of shoreline. This caused the wave height
to grow very tall and thus inundate more land.(4)
The original quake happened at 3:36 AM Universal Time
(UT, Greenwich Mean Time). At 5:36 AM UT a warning was
issued to California that a tsunami was possible.
By 6:44 AM UT the sheriff of Crescent City had been
notified that it was definitely on its way.
Evacuation was begun at 7:08 AM UT. All of the
coastal front areas were evacuated. One hour later
the waves arrived.(1) The first wave crested four meters
(13 feet) above low tide. The second wave was smaller.(3)
The third and fourth waves damaged low lying areas
around the south beach, with the third running inland
500 meters (546 yds).
Thirty city blocks were flooded by these waves. Single
story wood framed houses were either badly damaged or
destroyed. After the first two waves had passed some of
the townspeople believed the threat was over, and returned
to their homes and businesses.
The tragedy
One such group of seven returned to a tavern to
begin cleanup. While working, they decided to have a drink. They
were trapped in the building by the third wave and
five of them drowned.(1)
Other people returned to the shore to watch the ocean.
They were surprised by a fifth wave,
which crested six meters (20 feet) higher
than the low tide level mainly because
the tide was at its high level by this time.
Twelve people lost their lives to this wave.(3)
Learn more about the 1964 Good Friday Great Alaskan Earthquake
Other sites of interest:
Windows to Arizona Geology
United States Geological Survey Report on
the
Alaskan quake.
Detailed information on
damage
caused by the 1964 Alaskan tsunami
including damage to boats, deaths per town,
property damage values and locations and other
phenomenon along the US coast, in Hawaii
and Japan.
Detailed information listing
Pacific-wide tsunami waves heights,
their impact location by latitude and longitude, and
height.
The information covers Alaska, a few locations in Canada,
and many more in Washington, Oregon,
California, and Hawaii. Some information from Mexico, El Salvador,
Costa Rica, Panama, and Antarctica is also included,
as are islands in the Pacific, and Japan.
Map showing the
travel times of this tsunami.
Dr. George Pararas-Carayannis
complete guide to tsunamis.
Credits
With many thanks to the following sources:
Macklin, T. for
photos by his brother.
1) Bolt, B., 1993, Earthquakes. W.H.Freeman and Company.
2) Christensen, D.
http://www.aeic.alaska.edu/Seis/64quake/quake_description.html
3) Lutgens, F. and Tarbeck, E., 1995, Essentials in Geology. Prentice Hall.
4) Pipkin, B. and Trent, D., 1997, Geology and the Environment. West/Wadsworth.
5) Sokolowski, T.
http://wcatwc.gov/64quake.htm
6) United States Geological Survey.
http://wwwneic.cr.usgs.gov/neis/eqlists/USA/1964_03_28.html
Page by Nievita Bueno Hartness
Last Updated 12/06/2001
