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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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