Geoscience Reference
In-Depth Information
Seismic station
Tide gauge
DART buoy
THRUST coverage
North
America
60
˚
Palmer
Tokyo
Pacific Tsunami
Warning Center
30˚
Guam
Wake Island
Hawaii
South
America
0˚
Papeete
Australia
Valparaiso
-30˚
Easter Island
Wellington
-60˚
120˚
150˚
180˚
-150˚
-120˚
-90˚
-60˚
Location of seismic stations and tide gauges making up the Pacific Tsunami Warning System, buoys forming NOAA's DART network, and area of
potential coverage of the THRUST satellite warning system (sources: Bernard, 1991; González, 1999; <http://vishnu.glg.nau.edu/wsspc/
tsunami/HI/Waves/waves00.html> [cited 2000, now defunct]
Fig. 10.17
and linked to satellites for rapid communication
(Figure 10.17). The project is known as the Deep-
Ocean Assessment and Reporting of Tsunami (DART).
The bottom transducers can detect a tsunami with
heights of only 1 cm in water depths of 6000 m. The
United States also warns its west coast separately.
The West Coast/Alaskan Tsunami Warning Center
(WC/ATWC) in Palmer, Alaska, was established after
the 1964 Alaskan earthquake to provide tsunami
warnings to coastal areas of Alaska following local
earthquakes. In 1982, the Center's mandate was
extended to include the coasts of California, Oregon,
Washington, and British Columbia. Alarms are trigger-
ing by any sustained, large earthquake monitored at
eight seismometers positioned along the west coast of
North America. Regional warnings can be issued
within fifteen minutes of the occurrence of any earth-
quake having a surface magnitude greater than 7.
Localized earthquakes pose dilemmas in many
countries. Separate warning systems exist for Hawaii,
Russia, French Polynesia, Japan and Chile. The Russian
warning system was developed for the Kuril-
Kamchatka region following the devastating Kamchatka
tsunami of 1952. This system is geared towards the
rapid detection of the epicenter of coastal tsunamigenic
earthquakes, because some tsunami here take only
20-30 minutes to reach shore. In French Polynesia in
1987, a system was developed by the Polynesian
Tsunami Warning Center at Papeete, Tahiti, to detect
both near- and far-field tsunami. The system uses
the automated algorithm TREMORS and calculates the
expected tsunami height from any epicenter in the
Pacific. Near-field tsunami are a threat in Japan, espe-
cially along the Sanriku coastline of north-eastern
Honshu where only 25-30 minutes lead time exists
between the beginning of an earthquake and the arrival
at shore of the resulting tsunami. The P-wave for any
local earthquake can be detected within seconds using
an extensive network of high-frequency and low-magni-
fication seismometers. Within the next two minutes, the
height of the tsunami along the adjacent coastline can
be predicted using graphic forecasting models based
upon the size of prior earthquakes and the distance
to their epicenters. Finally, Chile, being the source
of many teleseismic tsunami, does not rely upon the
Pacific Tsunami Warning System, because this does not
