Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters - by Dr. George Pararas Carayannis

 

Tsunami, Earthquakes, Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters

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Tsunami

Frequently Asked Questions About Tsunami and the International Tsunami Warning System

George Pararas-Carayannis

(Excerpts from an educational information packet prepared, under contract, for UNESCO for the World Conference on Natural Disaster Reduction Yokohama, Japan, 23-27 May 1994)

Frequently Asked Questions About Tsunami and the International Tsunami Warning System

Questions fréquemment posées au sujet de Tsunami et du Système d'Alerte International de Tsunami (En Français)

Preguntas hizo con frecuencia acerca de Tsunami (En Espagnol)

What generates tsunami?
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 was established?
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 (ICG/ITSU)?
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)?

What is 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?

What generates tsunami?
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 was established?
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 (ICG/ITSU)?
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)?

What is 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?

GENERAL INFORMATION

Frequently Asked Questions About Tsunami

What generates tsunami?

Tsunami(s), 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.

Why 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 force.

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.

The May 1960 Chilean Tsunami?

The largest 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)

What was so devastating about the Great Alaskan Earthquake of 1964?

The Great 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.

(Photograph 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.

What did people do before the International Tsunami Warning System was established?


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).

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 (ICG/ITSU)?

(Excerpts from articles published in Sea Frontiers and elsewhere)

Introduction

The International 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.

(1960 tsunami damage at Hilo, Hawaiian Islands)

Historical Background

The great 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 organization.

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.

ITIC Mandate

ITIC's mandate 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

Additional 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.

Research and Data Collection Responsibilities

ITIC maintains 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.

Visiting Scientists Program

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.

With Member 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.

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?


ITWS 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)

Effects 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.)

Why is the ITIC visiting scientists program successful?


Under 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.

Are Scientific Tsunami Workshops and Educational Seminars and Conferences held?


Scientific 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.

Are there any Educational Materials for Children and the General Public?


An illustrated 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)?


What is a seismic station?

A seismic 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 share data.

What is a tide station?

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.

How many seismic and tide stations are used by ITWS?

The International 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.

What happens when a major earthquake or other disturbance prompts a tsunami? How does the International Tsunami Warning System Work?

Functioning 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.

How are watches and warnings disseminated?

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 gauges.

Watch bulletins 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.

What are the Capabilities and Limitations of the International Tsunami Warning System (ITWS)?

A tsunami 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.

What is a WDC?

A WDC is the acronym for a World Data Center.

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