from an educational information packet prepared, under contract, for UNESCO for the
World Conference on Natural Disaster Reduction Yokohama, Japan,
23-27 May 1994)
a seismic station? What is a tide station? How many seismic and
tide stations are used by ITWS? What happens when a major earthquake
or other disturbance prompts a tsunami? How the Tsunami Warning
System Works? How are Tsunami watches and warnings disseminated?
What are the Capabilities and Limitations of the International
Tsunami Warning System (ITWS)? What is a WDC?
Why are tsunami so destructive?
What did the May 1960 Chilean Tsunami Do?
What was so devastating about the Great Alaskan Earthquake and
Tsunami of 1964?
What did people do before the International Tsunami Warning System
What is the International Tsunami Warning System(ITWS)?
What is the
International Tsunami Information Centre (ITIC)?
What is the
International Coordination Group for the Tsunami Warning System
Why is the International Tsunami Warning System (ITWS) and the
International Tsunami Information Center (ITIC) one of the most
successful international scientific programs in disaster reduction?
Why is the ITIC visiting scientists program successful?
What is the International Tsunami Warning System(ITWS)?
Questions About Tsunami
also called seismic sea waves, are a series of waves generated
by large, violent earthquakes occuring near the ocean. Not all
earthquakes generate tsunamis.By far, the most destructive tsunamis
are generated from large shallow earthquakes with an epicenter
or fault line near or on the ocean floor. Vertical displacements
of the earth's crust along the rupture, resulting from such earthquakes,
can generate destructive tsunami waves which can travel across
an ocean spreading destruction across their path. Similar displacements
of the ocean floor can also be produced by volcanic eruptions
and submarine avalanches, or submarine landslides. However, these
sources are considered as point sources and , although destructive
locally, the energy of the waves is rapidly dissipated as they
travel across the ocean.
The wave crests of a tsunami may be a hundred kilometers or more
apart as they travel across the ocean. The height from trough
to crest may be only a few centimeters or meters in the open
ocean. A tsunami cannot be felt aboard ships in deep water.
are tsunami so destructive?
As the tsunami
enters the shoaling water near the coast, its velocity decreases
and its height increases. It is in these shallow waters that
tsunamis become a threat to life and property, for they can crest
to heights of of more than 30-50 meters and strike with devastating
Finally, terminal height or run-up of the tsunami at the point
of impact will depend on how the energy is focused, the travel
path of the waves, the coastal configuration, and the offshore
topography. Tsunami run-up is the vertical distance between the
maximum height reached by the water on shore and the mean sea
level surface. Tsunamis are among the most terrifying natural
hazards known to man. They have been responsible for tremendous
loss of life and property throughout history.
earthquake in recorded times in the southern hemisphere occurred
on May 22, 1960 along the Chile Trench, an area of crustal subduction
known for large historic earthquakes and tsunamis. The greatest
damage was caused by the tsunami waves which were destructive,
not only locally in Chile, but throughout the Pacific. There
was tremendous loss of life and property in Hawaii, Japan and
elsewhere in the Pacific. (Aerial Photo of the May 1960 tsunami damage
at Isla Chiloe, Chile)
Alaskan Earthquake of March 28, 1964 was the largest earthquake
to hit the northern hemisphere in recorded history. Its magnitude
was 8.3. It affected an area that was almost one thousand miles
long and more than two hundred miles wide. It affected a great
part of Alaska from Valdez,the entire Prince William Sound, Kenai
peninsula, Kodiak Island all the way to the Trinity Islands.
The earthquake itself caused areas to be lifted by as much as
30 feet while many other areas subsided greatly. There was tremendous
destruction from the earthquake throughout the populated regions
of Alaska. The eartquake generated a great tsunami which was
extremely damaging, not only in Alaska, but along Vancouver Island,
and in Northern California and Hawaii.. Hardest hit was Crescent
City, California, where eleven persons lost their lives.
of the 1964 tsunami damage at Seward, Alaska)
The tsunami waves affected
the entire California coastline, but were particularly high from
Crescent City to Monterey with heights on the open coast ranging
from 7 - 21 feet. At Santa Cruz Harbor, the tsunami wave reached
as high as 11 feet, sinking a hydraulic dredge and a 38 foot
cabin cruiser and causing minor damage to the floating docks.
Damage in San Francisco Bay was largely to pleasure boats. The
highest damage was reported from marinas in Marin County where
strong currents induced by the tsunami caused boats and floating
piers to break loose and strike other craft.
Damage at Noyo Harbor was primarily to floating piers and to
commercial fishing vessels. Also, damage occurred in Los Angeles
and Long Beach Harbors. The estimated losses elsewhere along
California were between $1,500,000 and $2,375,000 (1964 dollars),
while at Crescent City tsunami damage was estimated at $7,414,000.
The maximum wave at Crescent City was approximately 20 to 21
feet. Crescent City Harbor is one of the oldest. Lumbering and
timber products are the major industries. The first of the four
tsunami waves that struck Crescent City caused no significant
damage other than flooding. The second and third waves were smaller
than the first. The fourth was the largest of the waves and was
preceded by a withdrawal of the water which left the inner harbor
almost dry. The fast moving fourth wave capsized 15 fishing boats
in the harbor. Three other boats disappeared, and eight more
sunk in the mooring area. Several other boats were washed onto
the beach. Extensive damage was inflicted to the piers. The tsunami
waves covered the entire length of Front Street, and about thirty
blocks of Crescent City were devastated. Lumber, automobiles,
and other objects carried by the waves were responsible for a
good portion of the damage to the buildings in the area. Fires
started when the largest tsunami wave picked up a gasoline tank
truck and slammed it against electrical wires. The fire spread
quickly to the Texaco tank farm, which burned for three days.
did people do before the International Tsunami Warning System
Before the International
Tsunami Warning System (ITWS) went into effect there were not
effective warning systems to alert the countries of the Pacific
of an impending tsunami threat.The tsunamis often struck populated
areas with no warning or evacuation. The data was not always
shared among nations of the Pacific. Communication channels had
not been established for the sharing of such data.
The lack of a warning system was responsible for extensive loss
of life and property. It was the great destruction caused by
the May 1960 Chilean tsunami which prompted a large number of
countries and territories to join the Pacific Tsunami Warning
System (TWS), at least by contributing data and information.
It was the great Alaskan earthquake of 1964 which generated a
devastating tsunami that precipitated the need for an International
Tsunami Warning System (ITWS).
articles published in Sea Frontiers and elsewhere)
Tsunami Warning System in the Pacific (ITWS) and the International
Tsunami Information Centre (ITIC) is one of the most successful
international scientific programs in disaster reduction. With
support from the United States and other Member Nations and with
the continuous sponsorhip and coordination by the Intergovernmental
Oceanographic Commission (IOC) of UNESCO, the program has been
in operation for more than 30 years. The program has the direct
humanitarian responsibility of mitigating the effects of tsunami
disasters by saving lives and protecting property. It has been
made possible by UNESCO/IOC's involvement, the generous contributions
by the United States and through the active coordination of the
International Tsunami Information Centre (ITIC) in Honolulu,
Hawaii. Also, this successful disaster reduction program has
become possible because of the interest, generosity, and active
participation of many UNESCO/IOC Member Nations.
damage at Hilo, Hawaiian Islands)
destruction and loss of life caused by the May 1960 Chilean tsunami
prompted a large number of countries and territories to inquire
about joining in a Pacific Tsunami Warning System (TWS). The
great Alaskan earthquake of 1964 generated another devastating
tsunami that affected a good part of the Pacific. This tsunami
disaster focused additional attention to the need for an International
Tsunami Warning System under the auspices of a United Nations
In 1965, UNESCO/IOC, recognizing the importance of providing
timely warnings of the approach of potentially-catasthrophic
tsunamis in the Pacific Ocean, accepted the offer of the United
States of America to undertake the expansion of its existing
National Tsunami Warning Center in Honolulu, Hawaii, to become
the International Tsunami Information Centre (ITIC). The U.S.Tsunami
Warning Center in Honolulu, Hawaii (PTWC) became the headquarters
of the International Pacific Tsunami Warning System. At the same
time, UNESCO/IOC, accepted the generous offers of other UNESCO/IOC
member countries to integrate their existing facilities and communications
into this System. The existing U.S. Warning Systems in Hawaii
and in Alaska (ATWC) were integrated with the Systems of Japan,
USSR, Chile, and of other regional centers, and became a truly
International Tsunami Warning System(ITWS).
The International Tsunami Information Centre (ITIC) was signed
into effect by unanimous decision during UNESCO/IOC's
special meeting at Honolulu, Hawaii, April 27-30, 1965. At the
same time, the International Coordination Group for the Tsunami
Warning System (ICG/ITSU) was established as a subsidiary body
of IOC. Represented at this special UNESCO/IOC organizational
meeting were Canada, Chile, Republic of China, France, Japan,
Mexico, New Zealand, Peru, Republic of the Philippines, United
States of America, Union of Soviet Socialist Republics, and Western
Samoa. Many international scientific, national and international
organizations were represented also, such as the Inter-American
Geodetic Survey, the Tsunami Committee of the International Union
of Geodesy and Geophysics, (IUGG), the World Meteorological Organization
(WMO), the Ryuku Islands, and the Trust Territory of the Pacific.
ITIC and ICG/ITSU were formally established in accordance with
the UNESCO/IOC Resolution #1 entitled "International Aspects
of the Tsunami Warning System in the Pacific", adopted in
Paris at the Fourth Session of UNESCO General Assembly, on November
12, 1965. Thus, UNESCO/IOC played a very important lead role
in beginning a very successful and cost-effective, disaster warning
and mitigation program, twenty-five years before the International
Decade on Natural Disaster Reduction (IDNDR) was initiated.
Under the direction and guidance of UNESCO/IOC, the International
Tsunami Information Centre was instrumental in increasing dramatically
the membership of ICG/ITSU. From the original six nations that
joined ICG/ITSU in 1965, twenty-eight nations are presently members
of the International Tsunami Warning System. The System utilizes
numerous seismic and tidal stations and satellite communications
throughout the Pacific Ocean and disseminates, on a real-time
basis, tsunami watches and warnings to all the countries and
territories of the entire Pacific Basin. Many more UNESCO/IOC
Member Nations are expected to join ICG/ITSU and the Tsunami
Warning System, in the near future.
and functions evolved and expanded over the years. Initially,
ITIC was given the general mandate of mitigating the effects
of Tsunamis throughout the Pacific by supporting Member States
of the ICG/ITSU in developing and improving preparedness for
tsunamis by monitoring and seeking to improve the Tsunami Warning
System for the Pacific; by gathering and disseminating knowledge
on tsunamis, and fostering tsunami research; by bringing a knowledge
of the Tsunami Warning System and ITIC to non-member states,
and information on how to become participants through ICG/ITSU;
and by conducting post-disaster surveys for the purpose of documentation
and understanding of the tsunami disaster. Later, the functions
and responsibilities of ITIC were expanded to include a number
of other tsunami disaster preparedness and education activities,
aimed at disaster reduction.
ITIC functions include: a) Insuring the dissemination of tsunami
watches and warnings and the collection of tsunami information
on a real-time basis; b) Giving technical advice on the equipment
required for an effective warning system and providing assistance
in the establishement of national warning systems; c) Making
periodic studies and assessment visits to developing countries
in order to evaluate their instrumentation requirements, assess
their performance, offer advice as appropriate, and suggest avenues
for assistance; d) Evaluating the performance of the Tsunami
Warning System with regard to communications, data networks,
and the dissemination of warnings; e) Coordinating the development
of the observing system which provides the information necessary
for the issuance of effective tsunami warnings to those nations
wishing to receive such messages.
a complete library of publications related to tsunamis. The Centre
also maintains a full file of data related to tsunamis as obtained
from WDC's and from the real-time Tsunami Warning System, to
serve as part of the basis for the information services, materials
for visiting scientists, and data compilations and summaries.
To accomplish this task, ITIC maintains close contact with IUGG
(International Union Of Geodesy and Geophysics) and many other
national and international scientific organizations. ITIC continuously
monitors the results of current tsunami research in order to
find applications which may result in the improvement of the
International Tsunami Warning System.
One of the
most successful ITIC programs has been the Visiting Scientists
Program. With Member States' and UNESCO/IOC support, ITIC conducts
this training program by providing facilities at the Centre and
by arranging for the exchange of scientists among UNESCO/IOC
member countries. ITIC has trained numerous scientists of Member
States who, upon returning to their respective countries, train
and educate others on tsunami programs and procedures, thus ensuring
the continuity and success of the program.
Commitment to Education,
Preparedness and Disaster Reduction.
States' and UNESCO/IOC support, ITIC organizes and conducts scientific
workshops and educational seminars aimed towards tsunami disaster
education and preparedness. These training workshops are usually
conducted in conjunction with IOC/ITSU meetings which are held
every two years in a member state for the purpose of coordinating
and reviewing the activities of the International Tsunami Warning
System (ITWS). Also, with U.S. and UNESCO/IOC support, ITIC publishes
an informational and educational Newsletter on a regular basis.
This Newsletter is distributed to interested individuals, scientists
and institutions in approximately seventy countries. Additionally,
with UNESCO/IOC and Member Nations' support, ITIC disseminates
appropriate compilations of tsunami information and data. Such
publications may include regional tsunami catalogs and yearly
summaries of tsunamis. In recent years, emphasis has been placed
on the preparation of educational materials such as textbooks
for children and instructions for teachers. Teaching with the
help of these books has been already implemented in Chile. The
results have been very encouraging. Plans are being made by other
UNESCO/IOC Member Nations to implement similar educational programs
into their school systems. Through such continuous efforts, UNESCO/IOC
Member States and the International Tsunami Information Centre
have strongly supported the goals and objectives of IDNDR and
have contributed effectively in defining realistic parameters
and plans for IDNDR implementation, particularly in developing
countries. ITIC has been a strong supporter of the development
of educational and public preparedness programs that can result
in further mitigation of the tsunami disaster in the future.
and ITIC are one of the most successful international scientific
programmes in disaster reduction for many reasons. Among them:
a) Insures dissemination of Tsunami Warnings throughout the Pacific,which
result in reduction in loss of life and property.
(The specific numbers of lives saved or property preserved cannot
be quantitatively estimated. However, since the formation of
ITWS and ITIC all major tsunami events have been detected and
warnings have been disseminated. All the tsunami data has been
documented. Without these warnings and the international cooperation
and communications established byITWS and ITIC, the death toll
could be substantially higher. Without the data collected by
ITWS and ITIC our understanding of the tsunami disaster and its
effects would not be as comprehensive as it is. Without this
understanding and documentation, operational techniques of forecasting
and warning could not be as effectively implemented.
It is estimated that
since the establishment of ITIC and the International Tsunami
Warning System, more thant thirty years ago, thousands of lives
have been saved and millions of dollars in property damage have
been averted because of the planning promoted by ITIC, and ICG/ITSU
Member Nations. However, specific figures cannot be provided)
of the 1999 Earthquake and Tsunami to coastal city in the Sea
of Marmara, Turkey.
b) Encourage applied type of research focusing on practical applications
of effective disaster warning services which directly benefit
the countries of the Pacific.
(For example such research has involved mathematical modelling
which has resulted in tsunami travel time charts and tsunami
energy distribution, giving accurate prediction of the destructive
wave arrival, height information, and extent of expected inundation.
These applied research results are then used by planners and
policy makers in establishing criteria for evacuation, and for
coastal zone management.Such applications result in greater safety
and reduction of the effects of the tsunami disaster. Hilo, Hawaii,
is an example of such research that resulted in better zoning
and standards of construction.)
c) Promote the exchage of scientific and technical personnel
and data among the participating nations.
(This forms the basis for disaster assessment and reduction in
each of the participating countries. Training of scientists and
technical personnel results in better informed officials who
in turn institute programs of training and education which result
in reduction of the hazard in their own countries).
d) ITWS and ITIC contribute effectively in the preparation of
materials for public education and preparedness for the tsunami
disaster in all the participating nations of the Pacific.
(ITIC has spearheaded such educational efforts by publishing
educational materials, brochures, children's books which are
used by member nations in school and community programs in the
countries that participate in the Tsunami Warning System.)
the guidance and funding of IOC, ITIC has a visiting scientist
Program that trains invited scientists, particularly from developing
countries, in the methods, procedures, and techniques used in
the Tsunami Warning System. Additionally ITIC coordinates with
such scientists on-going applied research, data collection and
archiving, and provides training in tsunami disaster preparedness
and in public education. These scientists are selected carefully
from countries that have specific needs for improving their tsunami
disaster program. Trained scientists returning to their countries
are assigned follow up responsibiities for further training of
colleagues and associates. Progress reports are prepared and
objectives defined. Thus the program reaches many more people
than what the funding allows. In addition, the program assures
coherence, continuity and uniformity of the ITWS methods and
procedures. In addition it builds good will and results in very
tangible benfits in disaster mitigation on a lerger scale because
it opens avenues of communication and coordination, not previously
available. Although only 50-60 scientists may have received such
direct training through the program over the years, the results
are far reaching in that hundreds more have been trained subsequently
in different countries by the ITIC trained scientists.
workshops, educational seminars and conferences are held every
two or four years. Such workshops are very successful and cost-efficient
as they are scheduled in conjuction with ICG/ITSU coordination
meetings and conferences. Whenever possible these workshops and
training seminars are collocated also with meetings and workshops
of other organizations, such as IUGG, The Tsunami Society and
the International Society for Disaster Mitigation, to ensure
maximum participation and qualified instructors.
children's book on the tsunami disaster has been prepared by
ITIC and disseminated by UNESCO-IOC. Numerous other publications,
brochures and pamphlets have been prepared. ICG/ITSU and ITIC
have coordinated the preparation of textbooks for 2nd to 4th
grade students as well as up to 6th grade students. Teaching
with the help of these books have been implemented successfully
in Chile, and many other countries. Theeducational programs have
also reached the parents of the students as well and have been
very well received by many Pacific communities concerned with
the tsunami risk.This effort is disaster preparedness at the
grass-root level and has had far reaching effect in the communities,
simply because of its introduction into the school system. There
are plans to expand the program in many other Pacific countries.
Similarly there are plans to prepare educational materials and
methodological instructions for teachers.
The books for children and the different educational publications
are on the Tsunami Warning System. They explain what causes tsunamis,
how tsunamis travel and what happens when they reach the shore.
The books and brochures explain tsunami safety rules and what
people in coastal areas should do in times of emergency. Other
workbooks about disasters have been prepared explaining earthquakes,
tsunamis, volcanoes, other natural hazards, and safety measures
in reducing the effects of disasters.
What is the International Tsunami Warning System(ITWS)?
station is a laboratory that has equipment that can detect, monitor
and record earthquakes locally or anywhere in the world. It has
different type of seismic instruments that can record earthquake
waves traveling trough the interior of the earth and its surface.
A functioning seismic station must be able to perform many different
functions and determine important parameters of an earthquake
such as magnitude, depth, and epicenter.It must have the ability
to communicate effectively with other seismic stations and to
A tide station
has one or more calibrated instruments, called tide gauges, which
have the ability to measure long and short term changes in sea
level from astronomical tides or long period waves such as tsunami
waves of surges. Tide stations in the ITWS telemeter their data
via satellite to PTWC and other regional warning centers.
Tsunami Warning System makes use of an extensive seismic and
tide gauge network. However, it makes primary use of 31 seismic
stations, and more than sixty tide stations which have the ability
to transmit their data immediately and in real time to the headquarters
at the Pacific Tsunami Warning Center in Hawaii.
of the System begins with the detection of an earthquake which
has a magnitude and location that make it potentially capable
of generating a tsunami. The earthquake has to be of sufficient
magnitude to trigger the alarm attached to the seismograph at
the station where it is being recorded. The alarm thresholds
are set so that ground vibrations of the amplitude and duration
associated with an earthquake of approximate magnitude 6.5 or
greater on the Richter Scale anywhere in the Pacific region will
cause them to sound. Personnel at the station immediately interpret
their seismographs and send their readings to the Pacific Tsunami
Warning Center (PTWC)., in Honolulu, which are the headquarters
for the international system (ITWS). Upon receipt of a report
from one of the participating seismic observatories or as a consequence
of the triggering of their own seismic alarm, PTWC personnel
send messages requesting data from the observatories in the system.
When sufficient data
has been received so that the earthquake can be located and the
magnitude computed, a decision is made as to further action.
If the earthquake is strong enough to cause a tsunami and is
located in an area where this is possible, participating tide
stations near the epicenter are requested to monitor their tide
are issued to the dissemination agencies for all earthquakes
of magnitude 7 or greater occurring in the Aleutian Islands and
all earthquakes of magnitude 7.5 or greater occurring elsewhere
in the Pacific. A watch may also be disseminated by PTWC upon
the issuance of warnings by the regional warning centers. Since
the regional systems use different criteria for their disseminations,
a watch may at times be issued for earthquakes with magnitude
less than 7.5.
When reports from tide stations show that a tsunami poses a threat
to the population in a part or all of the Pacific, a warning
is transmitted to the dissemination agencies for relay to the
public. These agencies then implement plans to evacuate people
from endangered areas. If the tide station reports indicate that
either a negligible tsunami or no tsunami has been generated,
PTWC issues a cancellation.
Tsunami watches and warnings are disseminated by PTWC to over
100 dissemination points scattered throughout the Pacific Basin
under the varying control of the member states with general guidance
from IOC, and the ICG/ITSU. These major dissemination points
are responsible for further dissemination to hundreds of other
points within their geographical jurisdictions.
The major dissemination responsibility of the ITWS is the tsunami
watch and/or warning. The dissemination program is a sophisticated
cooperative venture using existing national and international
communication facilities. The communications systems to over
100 dissemination points along with over 100 data gathering stations
are tested monthly with dummy messages. The tests are monitored
for minimum message travel times. These dissemination points
in turn disseminate to many more points in their respective local
areas. ITIC has played a significant role in coordinating cooperation
among nations in the ITWS and establishing communication requirements,
procedures, and monitoring the results.
originates in or near the epicentral area of the earthquake that
creates it. It propagates outward in all directions at a speed
that depends on ocean depths. In the deep ocean the speed may
exceed 600 km/s; thus, the need for rapid data handling and communication
becomes obvious. Because of the time spent in collecting seismic
and tidal data, the warnings issued by PTWC and ATWC (headquarters
for international warnings) cannot protect areas against local
tsunamis in the first hour after generation; for this purpose,
regional warning systems have been established in some areas.
The regional systems generally have data from a number of seismic
and tide stations telemetered to a central headquarters. Nearby
earthquakes are located, usually in 15 minutes or less, and a
warning based on seismological evidence is released to the population
of the area. Since the warning is issued on the basis of seismic
data alone, watches or even warnings will occasionally be issued
when tsunamis have not been generated. Since they are issued
only to restricted area and confirmation of the existence or
nonexistence of a tsunami is rapidly obtained, dislocations of
populations are minimized. To limit the number of agencies to
be contacted, warnings are generally issued to only one agency
in each country, territory, or administrative area.
Dissemination agencies have the continuing responsibility for
educating the public concerning the dangers of tsunamis and for
developing safety measures that must be taken to avoid loss of
life and to reduce property damage. The agencies are encouraged
to develop emergency plans for all threatened localities, clearly
delineating areas of possible inundation. Evacuation routes are
designated, safe areas marked, and the amount of advance warning
to insure evacuation from danger.
A WDC is
the acronym for a World Data Center.
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