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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EFFECTS OF TSUNAMI ON SOCIETY

George Pararas-Carayannis

By: G. Pararas-Carayannis from "Violent Forces in Nature", Ch. 11, Lamond Publications, 1986, p. 157-169. and from "Impact of Science on Society", Vol. 32, No.1, 1982, p 71-78) (Photos from ITIC archives)

(Note : Since 1982 , when this paper was written , there have been changes to the number of nations which particpate in the Tsunami Warning System. As of 2004 the number is 26 )

As far back as 1480 B.C. history records destruction by tsunami-huge ocean waves-with loss of life and property. Today population pressures on coastal areas bring more and more communities and installations under this threat. Tsunami warning systems employing advanced technological instrumentation require public education and confidence in government agencies for effectiveness.

Introduction


The tsunami is a series of ocean waves of very great length and period generated by impulsive disturbances of the earth's crust. Large earthquakes with epicenters under or near the ocean and with a net vertical displacement of the ocean floor are the cause of the most catastrophic tsunami. Volcanic eruptions and submarine landslides are also responsible for tsunami generation but their effects are usually localized. Although infrequent, tsunami are among the most terrifying and complex physical phenomena and have been responsible for great loss of life and extensive destruction to property. Because of their destructiveness, tsunami have important impact on the human, social and economic sectors of our societies. Historical records show that enormous destruction of coastal communities throughout the world has taken place and that the socioeconomic impact of tsunami in the past has been enormous. In the Pacific Ocean where the majority of these waves have been generated, the historical record shows tremendous destruction with extensive loss of life and property. In Japan, which has one of the most populated coastal regions in the world and a long history of earthquake activity, tsunami have destroyed entire coastal populations. There is also a history of tsunami destruction in Alaska, in the Hawaiian Islands, and in South America, although records for these areas are not extensive. The last major Pacific-wide tsunami occurred in 1960. Others have also occurred but their effects were localized.

We have witnessed in the last twenty years rapid growth and development of the coastal areas in most of the developing or developed Pacific nations. This is the result of a population explosion and of technological and economic developments that have made the use of the coastal zone more necessary than before. Fortunately, tsunami are not frequent events and therefore their effects have not been felt recently in all developing areas of the Pacific. History, however, has proved that although infrequent, destructive tsunami indeed do occur. A major Pacific-wide tsunami is likely to occur in the near future. Among the countries bordering on the Pacific, a number are not prepared for such an event while others have let their guard down. The social and economic impact of future tsunami, therefore, cannot be overlooked. The purpose of this paper is to provide an overview of the social and economic impact of past, recent and future tsunami, to examine tsunami hazard management, and to indicate the need for future planning, at least for the Pacific Ocean where tsunami frequency is high.

Historical record of destructive tsunami


The impact of tsunami on human society can be traced back in written history to 1480 B.C., in the eastern Mediterranean, when the Minoan civilization was wiped out by such waves. (photo of ancient city of Knossos, the capital of the Minoan civilization).

Japanese records documenting such catastrophes extend back to A.D. 684.(1) North and South American records have dated such events back to 1788 for Alaska and 1562 for Chile. Records of Hawaiian tsunami go back to 1821.

While most of the destructive tsunami have occurred in the Pacific Ocean, devastating tsunami have also occurred in the Atlantic and Indian Oceans, as well as the Mediterranean Sea. A large tsunami accompanied the earthquakes of Lisbon in 1755, that of the Mona Passage off Puerto Rico in 1918, and at the Grand Banks of Canada in 1929.

Most of the people in the Pacific countries live on or quite near the coast since the interior is often mountainous and most of the good flatland is in the form of coastal plains. Many of these countries have populations with a natural maritime orientation. For many of these countries, foreign trade is a necessity and some maintain large fleets of ships and have major port facilities. Many of the Pacific island countries and those with extensive continental coastlines depend also on transport by small coastal ships necessitating many small ports to facilitate inter-island and coastal trade as well. Countries like Japan, for example, maintain many ports and have extensive shipbuilding facilities, electric plants, refineries and other important structures.

Similarly, many of the other developing and developed countries of the Pacific have harbors as bases for their large fishing industries. Peru, for example, at the port of Callao near Lima, maintains a large fleet for anchovy fishing. Callao is located near a strong seismic and potentially tsunamigenic region. Finally, when we also note that a number of coastal sites throughout the Pacific have begun aqua cultural industries and canneries, we can only conclude that this combination of factors makes these developed and developing Pacific islands and continental Pacific nations socially and economically vulnerable to the threat of tsunami. The extensive coastal boundaries, the number of islands, the long coastlines of Pacific countries containing a number of vulnerable engineering structures, the numerous large ports, the productive fishing and aqua cultural industries and the great density of population in coastal areas can only place these countries in a very vulnerable position.

The vulnerability of Japan


For Japan, to give an example, where all the above-mentioned factors of vulnerability are present, the social and economic impact of a tsunami can be truly devastating. Along the Sanriku coast or in the Tohoku district of northern Honshu there are many flatlands with coastal embayments where large fishing and aqua culture industries have been established. Throughout history, entire settlements in such areas have been struck and destroyed by tsunami, often requiring their rebuilding and relocation.

The record reads as follows: a total of 65 destructive tsunami struck Japan between A.D. 684 and 1960. As early as 18 July 869 the Sanriku coast was hit by a tsunami resulting in loss of 1,000 lives and the destruction of hundreds of villages. On 3 August 1361, a tsunami destroyed 1,700 houses in this same area. On 20 September 1498 1,000 houses were washed away and 500 deaths resulted from a tsunami which struck the Kii peninsula. Kyushu was struck by a destructive tsunami in September 1596. Great loss of life occurred on 31 January 1596 from a tsunami on the island of Shikoku, affecting also a number of regions in Honshu. In recent times, the great Meiji Sanriku tsunami of 15 June 1896 resulted in 27,122 deaths, thousands of injuries, and the loss of thousands of homes. On 3 March 1933 a tsunami in the Sanriku area reached a height of about thirty meters and killed over 3,000 people. injured hundreds more and destroyed approximately 9,000 homes and 8,000 boats. In December 1944, a tsunami in central Honshu caused almost 1,000 deaths and the destruction of over 3,000 houses. The Nankaido tsunami, on 21 December 1946, resulted in 1,500 deaths and the destruction of 1,151 houses.(2)

 

Tsunami strikes in Pacific

Tsunami have struck the Hawaiian islands repeatedly, causing great loss of life and immense damage to property. Most noteworthy of the recent Hawaiian tsunami is that of 1 April 1946 which inundated and destroyed the city of Hilo, killing 159 people. Other recent tsunami that have hit Hawaii are those of 1952,1957,1960,1964 and 1975.(3)

The most destructive Pacific-wide tsunami in recent times was that of May 1960, killing over 1,000 people in Chile, Hawaii, the Philippines, Okinawa and Japan, and causing tremendous loss of life and destruction to property. More recently, on 16 August 1976, a large earthquake in the Moro Gulf in the Philippines generated a destructive local tsunami which killed over 8,000 persons, leaving 10,000 injured and 90,000 more homeless. (4) On 12 December 1979, another earthquake centered on the state of Narino in the south-west corner of Colombia generated a tsunami that completely destroyed several fishing villages, taking the lives of hundreds of people and creating economic chaos in an already economically depressed region of that country. (5)
(photo of tsunami destruction at Seward, Alaska from 1964 tsunami)

Tsunami destruction has not been confined to Japan or to the Pacific Ocean. Destructive tsunami have occurred also in the Atlantic and Indian Oceans and in the Caribbean and Mediterranean seas. As mentioned earlier the violent eruption and explosion of the volcano of Santorini in the fifteenth century B.C. generated a tremendous tsunami which destroyed most of the coastal Minoan settlements on the Aegean sea islands acting as the catalyst for the decline of the advanced Minoan civilization. (6) Many more destructive tsunami have occurred in the Eastern Mediterranean since then.

In the region of the Indian Ocean, the violent explosion of the volcanic island of Krakatoa in August 1883 generated a thirty-meter-high tsunami wave that killed 36,500 people in Java and Sumatra. As recently as four years ago, a large earthquake in the Lesser Sunda Islands, Indonesia, on 19 August 1977 generated a destructive tsunami which killed hundreds of people on Lombok and Sumbawa islands along the eastern side of the Indian Ocean. (7)

The Atlantic region

Historical records also document considerable loss of life and destruction of property on the western shores of the North and South Atlantic, the coastal waters of north-western Europe, (8) and in the seismically active regions around the eastern Caribbean. Most noteworthy of the Atlantic tsunami was that associated with the Lisbon earthquake of 1 November 1755 which struck not only Portugal but Spain, Madeira, the Azores, France, the British Isles and the islands of the West Indies.

Tsunami have been reported frequently from southern Ireland, Wales, England, as well as from the northern regions of the Iberian peninsula. One of the most destructive of the tsunami in the Caribbean sea was the tsunami at Port Royal, Jamaica, on 7 June 1692 which, in combination with the earthquake, took 3,000 lives.

Other destructive events were the tsunami of 3 June 1770 and that of 7 May 1842 on the island of Hispaniola, the tsunami in the Virgin Islands on 28 December 1867, the tsunami in Jamaica on 14 January 1907 and the tsunami of 11 October 1918 in Puerto Rico."

The above is simply a brief overview of some large historical tsunamis. It is very difficult to comment specifically on the impact each event has had on each stricken area. However, it can be clearly concluded that natural catastrophes, such as tsunami, have far more important and long-term social and economic impacts than any historical or statistical record can show. Furthermore, the historical record does not prepare us for the potential damage that can now be caused by tsunami in the coastal areas of many developing or developed coastal countries where development has taken place in the last twenty years. Future tsunami will have a much more severe social and economic impact in these areas than that of past events. It is therefore important that these areas begin now to plan and prepare for such future events.

Planning for the tsunami hazard


There is very little that can be done to prevent the occurrence of natural hazards. Floods, droughts, earthquakes, hurricanes, volcanic eruptions and tsunami cannot be prevented. But humankind, being as adaptable as it is, has learned to live with all these hazards. In the past, we have taken a passive approach to hazards, justifying them as acts of God or nature about which we could do very little.

But while these natural disasters cannot be prevented, their results, such as loss of life and property, can be reduced by proper planning. To plan for the tsunami hazard, however, we must have a good understanding not only of the physical nature of the phenomenon and its manifestation in each geographical locality, but also of that area's combined physical, social and cultural factors. Some of these areas are more vulnerable to tsunami than others. Because tsunami frequency in the Pacific Ocean is high, most efforts in hazard management have concentrated in this area of the world. No matter how remote, the likelihood of a tsunami should be considered in developing coastal zone management and land use. While some degree of risk is acceptable, government agencies should promote new development and population growth in areas of greater safety and less potential risk. These agencies should formulate land-use regulations for a given coastal area with the tsunami risk potential in mind, particularly if such an area is known to have sustained damage in the past.

International protective and preventive measures established


Present protective measures involve primarily the use of tsunami warning systems employing advanced technological instrumentation for data collection and for warning communications. Countries like Japan, the Soviet Union, Canada, and the United States have developed sophisticated warning systems and have accepted the responsibility to share warning information with other countries of the Pacific.

In 1965, Unesco's Intergovernmental Oceanographic Commission (UNESCO/IOC) accepted the United States' offer to expand its existing tsunami center in Honolulu to become the Pacific Tsunami Warning Center (PTWC). Also established was an International Co-ordination Group (ICG/ITSU) and the International Tsunami Information Center (ITIC) to review the activities of the International Tsunami Warning System for the Pacific (ITWS). The Pacific Tsunami Warning System has become the nucleus of a truly international system. Twenty-two nations (the number is now 28) are now members of ICG/ITSU: Canada, Chile, China, Colombia, Cook Islands, Ecuador, Fiji, France, Guatemala, Indonesia, Japan, Republic of Korea, Mexico, New Zealand, Peru, Philippines, Singapore, Thailand, the United Kingdom (Hong Kong), the United States, the Soviet Union, and Western Samoa. Several non-member nations and territories maintain stations for the ITWS, and tide observers are also located on a number of Pacific Islands. The present system makes use of twenty-four seismic stations, fifty-three tide stations, and fifty-two dissemination points scattered throughout the Pacific Basin under the varying control of the member states. PTWC in Honolulu, operated by the United States National Weather Service, is the operational center for the system. The objectives of the ITWS are to detect and locate major earthquakes in the Pacific region, determine whether they have generated tsunami, and provide timely and effective information and warnings to the population of the Pacific region in order to minimize the effect of the hazards on life and property.


Functioning of the warning system

Functioning of the system begins with the detection by any participating seismic observatory of an earthquake of sufficient size to trigger the alarm attached to the seismograph at that station. Earthquakes of 6.5 or greater on the Richter scale are investigated. PTWC collects the data and, when sufficient data has been received, locates the earthquake and computes its magnitude. When reports from tide stations show that a tsunami poses a threat to the population in part or all of the Pacific, a warning is transmitted to the dissemination agencies for relaying to the public . The agencies then implement predetermined plans to evacuate people from endangered areas. If the tide station reports indicate that a negligible or no tsunami has been generated, PTWC issues a cancellation. In addition to the International Tsunami Warning System, a number of Regional Warning Systems have been established to warn the population in areas where tsunami frequency is high and where immediate response is necessary. Such regional tsunami warning systems have been established in the Soviet Union, Japan, Alaska and Hawaii. Vast areas exist, however, where tsunami cannot be adequately detected or monitored in time and the populations warned to prevent extensive loss of life.

Because of the rarity of large destructive tsunami, it is difficult to institute successful tsunami-prediction schemes for warning the public. However, we can make people aware of the potential hazard. Tsunami warnings are issued to the public for the purpose of convincing people to evacuate endangered areas. Ample time must be allowed for evacuation, which is a rather difficult procedure. Often the public does not understand the meaning of the warning signals and is not aware of the locations of endangered areas. Most people are reluctant to evacuate their homes and businesses, and their response to warnings in general may not be very good, particularly if a number of false alarms have been issued.

Hazard perception by the public

Tsunami hazard perception by the people of a coastal area is based on education and confidence in government agencies responsible for tsunami prediction. Overwarning, based on inadequate knowledge of the phenomenon or inadequate data on which to base the prediction, often leads to false alarms and lack of compliance with warning and evacuation attempts. Such false alarms result in a loss of faith in the capability of the system and result in reluctance to take action in subsequent tsunami events. Even if a tsunami prediction is based on valid information and data, warning and evacuation may not be sufficient to minimize the impact of tsunami on coastal populations . Hazard perception by the public is based on a technical understanding of the phenomenon, at least at the basic level, and a behavioural response stemming from understanding of the phenomenon and confidence of the public in the authorities. Fortunately, forecasting of tsunami in recent years has been quite good and the image of the tsunami warning system and its credibility has improved considerably. Forecasting, however, is not an exact science as the phenomenon itself is very complex and data on which the forecast is based may often be inadequate for certain areas.


Awareness through public education

A heightened community awareness of the potential threat of tsunami can be achieved through a public education programme. Civil defense authorities in each country can initiate such a public education programme consisting of seminars and workshops for responsible government officials, can publish informational booklets on the hazards of tsunami, and can co-ordinate with the communications media on the announcement of tsunami information. Other government agencies can take action also to mitigate future losses from tsunami. For example, government agencies can develop sound coastal management policies, which include zoning and planning for tsunami-prone coastal areas. Scientific organizations can undertake research and engineering studies in developing evacuation zones or engineering guidelines for building coastal structures. Audio-visual materials can be prepared for educating children in schools and the public in general. Brochures and pamphlets can be printed describing the tsunami warning system and what the public can do in time of tsunami warning. Internally, government agencies can streamline and co-ordinate their operating procedures and communications so they can perform efficiently when the tsunami threat arises. Procedures related to tsunami warnings should be reviewed frequently to define and determine better respective responsibilities between the different governmnent agencies at all levels.


Conclusion and recommendations

In spite of our technological improvements of the last two decades, we are still unable to provide timely warnings to many areas of the Pacific and none to other parts of the world. Improvements are necessary in communications cations to ensure that warning information is prompt and accurate. An increased degree of automation is necessary in handling and interpreting the basic data. Research is needed for example in the development of instrumentation such as deep-ocean sensors, which could be useful in early tsunami detection. Research is needed also in the real-time interpretation of seismic source parameters, which in turn may help in tsunami evaluation. Apparently more research is needed in improving our understanding of a tsunami interacting with the coast. Research can also lead to improvement of warning systems, to better land-use management of tsunami-prone coastal areas and to development of important engineering guidelines of critical coastal structures. In conclusion, the long-term objective should be for each country susceptible to the tsunami hazard to build its technical and scientific infra structures to meet the hazards of a disastrous event. The immediate objectives of each country should be to assess this hazard in terms of potential needs and available resources. Preparedness requires several capabilities, such as rapid identification of imminent tsunami, effective national and regional warning systems to alert coastal population and industries, and civil defense and community preparedness to respond to tsunami warnings. Finally, appropriate improvements in warning capability in the form of improved instrumentation for tsunami monitoring and for communications should be developed, both for effective warning and for increased knowledge as an aid to long-term protection.


Notes

1. Iida, D. Cox and G. Pararas-Carayannis, Preliminary Catalogue of Tsunamis Occurring in the Pacific Ocean, Honolulu, Hawaii Institute of Geophysics, University of Hawaii, 1967. (Data Report No. 5.)

2. Ibid.

3 G. Pararas- Carayannis.
Catalog of Tsunamis in Hawaii, Boulder, Colorado, World Data Center-A for Solid Earth Geophysics, 1977.

4. ITIC,
Tsunami Report, No. 1976-26, 1978.

5. G. Pararas-Carayannis,
"Earthquake and Tsunami of 12 December 1979 in Colombia", Tsunami Newsletter, Vol. 13, No. 1, 1980, pp. 1-9.

6. G. Pararas-Carayannis,
"The International Tsunami Warning System", Sea Frontiers, Vol. 23, No. 1, 1977, pp.20-7.

7. ITIC,
Tsunami Report, No. 1977-12, 1978.

8. W. Berninghausen,
"Tsunamis and Seismic Seiches reported from the Eastern Atlantic South of the Bay of Biscay', Bulletin of the Seismological Society of America, Vol. 54, No. I, 1964, pp.439-42.

9. Anonymous, Tsunamis and seismic seiches reported from the western North and South Atlantic and the coastal waters of Northwestern Europe, Washington, D.C., Naval Oceanographic Office, 1968.

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