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NOAA TSUNAMI WARNING SYSTEM RECEIVES HIGH MARKS
November
17, 2004— A U.S. Department
of Commerce gold medal is being awarded to both the NOAA
Pacific Marine Environmental Laboratory and the NOAA
National Data Buoy Center for their work on the Deep
Ocean Assessment and Reporting of Tsunamis (also known as DART),
a new moored buoy system that provides accurate and timely tsunami
warning information. The value of DART
was evident on Nov.
17, 2003, (just a month after the system was transferred from research
to operational mode), when a tsunami warning was cancelled because real-time
DART data showed that the tsunami would not be damaging. Canceling
this warning averted an evacuation in Hawaii,
saving the state an estimated $68 million in lost productivity.
The
Nov. 17 event was similar in magnitude to an event from the same region
in 1986,
which triggered a tsunami warning that resulted in the evacuation of Hawaii
coastal areas. The tsunami that ultimately struck the Hawaii coastline,
however, was less than a foot in height and caused no damage. The average
cost of lost business and productivity because of the evacuation was estimated
by the State of Hawaii’s Department of Business, Economic Development
and Tourism to be $40 million. The State of Hawaii’s response to
this most recent earthquake/tsunami cost about $68 million less (adjusted
for inflation) because, for the first time, real-time data were available,
and no evacuation was ordered.
"Although there was no tsunami produced by the 7.7
earthquake, it did trigger the buoy and gave NOAA the
first opportunity to test the system since it went operational in October
2003," said Eddie
Bernard, director of the NOAA PMEL in Seattle, Wash., where the system
was developed, designed and built. "The buoy system performed as
designed."
DART has
already (and will continue to) help scientists better understand and predict
tsunami behavior, which will reduce false alarms and enable officials
to make better informed decisions that will ultimately save lives and
property.
General
Tsunami Information
A tsunami is
a series of waves generated by any rapid large-scale disturbance of sea
water. Most tsunamis are generated by coastal or oceanic earthquakes,
but they can also be caused by volcanic
eruptions, landslides or meteor impacts. Waves radiate outward in
all directions from the disturbance and (in some cases) can propagate
across entire ocean basins. (Click NOAA image to right for a larger
view of tsunami coming ashore.)
In the deep ocean, a tsunami is barely noticeable and will only cause a shallow and slow ripple on the sea surface as it passes. As it approaches the land, however, tsunamis become much more of a hazard. When a tsunami approaches shallower waters near the coast, the waves slow down and become compressed, causing them to grow in height. Under the best case scenario, the tsunami comes onshore like a quickly rising tide and only causes gentle flooding in low-lying coastal areas. Under the worst case scenario, however, walls of water more than 100 feet high rush ashore causing large scale destruction and flooding — a cycle which may repeat itself many times before the hazard finally passes.
Tsunamis typically cause the most severe damage and casualties near their source (i.e., earthquake) where the waves are the highest. Nearby local coastal populations — often disoriented from the violent earthquake shaking — may have very little time to react before a tsunami is generated and should move inland and to higher ground immediately.
Larger, more
powerful tsunamis can cause destruction and casualties over a much wider
area — even across the entire Pacific Basin. However, because they
are generated by more distant earthquakes and will make landfall several
hours (as opposed to minutes) after an earthquake, NOAA and its partners
are able to warn the public about these large regional tsunamis several
hours before they strike, thus allowing adequate time for evacuation.
Tsunami
Damage
Although tsunamis are rare and unpredictable, they pose a major
threat to the coastal populations of the Pacific and other world oceans/seas.
According to the NOAA National Geophysical
Data Center, tsunamis have been responsible for taking more than 3,000
lives and hundreds of millions of dollars in property damage in just the
last 10 years. Although scientists can't accurately predict when and where
earthquakes will occur, NOAA can determine if a tsunami will be generated
from them and help people learn how best to protect
themselves and their families from harm. (Click NOAA image upper
right for a larger view of Tsunami destruction.)
NOAA'S
Role in the U.S. Tsunami Program
A
total of four NOAA offices contribute to the U.S. Tsunami Program: the
NOAA National Weather Service (i.e.,
tsunami warning centers and NDBC), NOAA
Research (i.e., PMEL), NOAA
Ocean Service (operates tide gauges used in tsunami monitoring) and
NOAA Environmental Satellites, Data
and Information Service (i.e., NGDC
stores
tsunami data). It is the first two that are being honored with a U.S.
Department of Commerce gold medal award — PMEL for researching
and developing DART
and the NOAA Weather Service for operating and maintaining DART. The NOAA
Weather Service also promotes tsunami education and awareness through
its voluntary TsunamiReady
Community program and hosts the International
Tsunami Information Center in Honolulu, Hawaii, for the Intergovernmental
Oceanographic Commission. (Click NOAA image to the right for a
larger view of NOAA researchers working on tsunami research.)
NOAA also oversees the National Tsunami Hazard Mitigation Program. Formed in 1996, NOAA and its partners (i.e., Federal Emergency Management Agency, the U.S. Geological Survey and the states of Alaska, Washington, Oregon, California and Hawaii) have combined research and education to make significant progress in tsunami mitigation, hazard assessment and warning guidance.
NOAA
National Weather Service Tsunami Centers
The NOAA Weather Service operates two tsunami warning centers
— the West Coast/Alaska Tsunami
Warning Center in Palmer, Alaska, which has warning responsibility
for Alaska, British Columbia, Washington, Oregon and California; and the
Richard H. Hagemeyer Pacific
Tsunami Warning Center in Ewa Beach, Hawaii, which conducts research
and monitors tsunamis for Hawaii and both U.S. and international interests
in the Pacific Basin. Both centers were
established in 1967 and 1949, respectively, after damaging tsunamis hit
those states. Together they are the operational centers of a vigilant
24-hour U.S. tsunami warning system for the Pacific Rim.
Both centers work closely with state emergency managers, the U.S. Geological Survey and the Federal Emergency Management Agency to mitigate potential tsunami hazards. The NOAA Tsunami Warning Centers continuously monitor data from seismological and tidal stations, evaluate earthquakes that have the potential to generate tsunamis and disseminate tsunami information and warning bulletins to government authorities and the public. Despite this, however, it was not until DART that NOAA was able to accurately detect, assess and forecast the threat tsunamis pose to coastal communities.
Deep
Ocean Assessment and Reporting on Tsunami
In 1997, the National Tsunami Hazard Mitigation Program provided funding
for DART
development. The DART project was developed by the NOAA PMEL and brought
into operational use by the NOAA NDBC in October 2003. The DART project
is an ongoing effort to maintain and improve the capability for the early
detection and real-time reporting of tsunamis in the open ocean. DART
also reduces costly false alarms — 75 percent of all warnings issued
since 1948 have been for non-destructive tsunamis yet the evacuation of
Honolulu in 1986 cost $40 million . (Click NOAA image to the right
for larger map of DART buoy locations.)
How
DART Buoys Work
The DART
systems consist of a network
of six anchored sea floor
bottom pressure recorders and companion moored surface buoys for real-time
communications. The buoy's sea floor sensor detects pressure changes caused
by an earthquake (or other disturbance) and transmits that data via an
acoustic link to the surface buoy. The data are then relayed via a NOAA
GOES satellite link to ground stations, which prepare the signals
for immediate dissemination to the NOAA Tsunami Warning Centers, the National
Data Buoy Center and Pacific Marine Environmental Lab.
NOAA
geophysicists use the data to determine the size of the wave, what areas
may be at risk, and if a watch or warning is necessary. The DART research
experience over the last 10 years indicates that these real-time systems
are capable of detecting deep ocean tsunamis with amplitudes as small
as one cm. (Click NOAA image to the right for a larger diagram
showing how DART buoy works.)
Future
of DART
When the program is completed in 2011, NOAA hopes to have expanded
the DART network to a total of 20 sensors. NOAA is also using the DART
data to develop inundation models
and evacuation maps,
which show how far inland tsunami flooding may reach (and possibly how
fast the flow of water might be and how long the inundation will last)
for the states of Alaska, Washington, Oregon, California and Hawaii. DART
is consistent with the other in situ Earth observing technology that is
being used to establish a Global Observing System
and is essential to fulfilling NOAA's
national responsibility for tsunami hazard mitigation and warnings.
Relevant
Web Sites
Tsunami
Data at NGDC
NOAA Weather Service Tsunami FAQ
FAQs from the Tsunami Hazard Mitigation Program
FAQs from the West Coast/Alaska Tsunami Warning Center
An Integrated Approach to Improving Tsunami Warning and Mitigation
NOAA HONORS UNIVERSITY OF CALIFORNIA AT SANTA BARBARA AS FIRST TSUNAMIREADY UNIVERSITY IN NATION
NOAA’s DART RIGHT ON TSUNAMI TARGET
Media
Contact:
Jana
Goldman, NOAA Research, (301)
713-2483 x 181 or Delores Clark,
NOAA Weather Service, (301) 713-0622