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Earthquakes, Hurricanes, Volcanic Eruptions, Climate Change and
other Natural and Man-Made Hazards and Disasters - Disaster Archaeology,
QUESTIONS ABOUT THE PNG TSUNAMI OF 17 JULY 1998
The following are answers
to frequently asked questions about what happened in Papua New
Guinea on July 17, 1998 and on how the effects of similar disasters
can be mitigated in the future.
QUESTION: Supposing PNG had been a member
of this system (the Pacific Tsunami Warning System), what would
have it meant in practical terms?
ANSWER: In practical terms, PNG membership
in the International Coordination Group for the Tsunami Warning
System in the Pacific (ICG/ITSU) under the auspices of UNESCO
and the Intergovernmental Oceanographic Commission (IOC) and
membership in the Pacific Warning System, would not have done
anything for the victims of the 17 July,1998 tsunami. Even if
PNG was a member and had received a warning about the earthquake,
this was a local event for which no tsunami warning could be
issued within a reasonable time frame to do anyone in the immediate
vicinity any good.
QUESTION: If membership in the Tsunami
Warning System could not help with the issuance of a warning,
why should PNG join?
ANSWER: PNG membership in the System
would not have saved the lives of the people in the vicinity
of Vanimo from this local disaster, because the Pacific Warning
Syatem cannor issue local tsunami warnings for such short-fused
disasters. Although a warning could not have been issued quickly
enough, what could have saved lives would have been a programs
of preparedness and public education. Only through such programs,
the adverse effects of such short-fused disasters can be averted
and mitigated. Such programs of preparedness are promoted through
membership in the System and the ICG/ITSU with frequent seminars,
dissemination of educational materials, training of scientists
and public officials of participating nations. IOC through ICG/ITSU),
and the International Tsunami Information Center (ITIC) hold
workshops and training program sponsored and funded by IOC, which
have trained hundreds of scientists and public officials, who
upon return to their countries implemented, through their government,
programs of public education and preparedness in addition to
operational plans of warning dissemination. These training programs
have been truly invaluable.
QUESTION: PNG being out of the System,
does it mean that there is actually no permanent monitoring of
the area where the tremor and the tsunami appeared? Does it mean
that this tsunami was in effect not detected by the current System?
Or does it mean that although detection took place, no warning
was dispatched to PNG authorities because they are not members.
ANSWER: Not so. The Pacific Tsunami
Warning Center in Honolulu and numerous seismic observatories
throughout the world, including the Port Moresby Geophysical
Observatory, recorded this event immediately right after it happened
and probably exchanged seismic data. The Port Moresby Observatory,
being so close to the earthquake epicenter, in fact, recorded
it first and its alarm went off first.
No Warning was issued
by the Pacific Tsunami Warning Center (PTWC) because the magnitude
of the earthquake was less than the threshold required for issuance
of a Pacific-wide warning. The Bismark Sea, being an almost inland
sea surrounded by numerous islands, does not pose a threat in
the generation of Pacific-Wide tsunamis. Historical data shows
that no Pacific-wide tsunamis have been generated from the Southwest
Pacific, even from the Solomon Islands area which indeed experiences
very large earthquakes. However, such local earthquakes are known
to cause often destructive tsunamis in the immediate area for
which, unfortunately, PTWC cannot issue warnings because of the
short time interval between the quake and the tsunami.
To the best of my knowledge,
PTWC does not issue regional watches or warnings unless the earthquake
magnitude exceeds the designated threshold and even then these
warnings are of limited use to the people in the immediate area.
You may wish to contact the scientist in charge at PTWC for additional
clarification or any changes in operational procedures. However
there is a definite need for further automation, streamlining
of the warning procedures and establishing a Regional Warning
Center in PNG which can handle such emergency situations. But
even Japan's sophisticated Regional Tsunami Warning System was
unable to issue warnings for the immediate area in the Sea of
Japan in 1983, or in Kobe in 1995 because of the short time interval.
QUESTION: How could a Regional Warning
System have been of help in the detection of a tsunami and the
issuance of a warning before it reached the shore?
ANSWER: Given the closeness of the earthquake
to the coast, the first tsunami wave arrived at the coastal villages,
probably within 1-3 minutes. A warning could not be disseminated
in that short time frame, regardless of resources, the existence
of a regional warning system, or membership in the Pacific Tsunami
Warning System. However, a warning could be of help to people
further away from the source.
QUESTION: How long would it take for a
Regional Warning Center to issue a tsunami warning for a local
ANSWER: Even with automated instrumentation
and automated computer analysis, it takes at least 2-3 minutes
for personnel at a seismic observatory to respond to a seismic
alarm and to evaluate the data and issue a warning. This is true
only if there is complete automation, 24-hour a day station coverage,
and a plan of action. To the best of my knowledge, both the Pacific
T the Alaska Tsunami Warning Centers presently have that capability
to process the data quickly. However, it takes at least another
4-5 minutes for the warning to be disseminated, even under the
most optimum circumstances. So, the process must be completely
automated. The technology for such automation exists.
QUESTION: Will an automated Regional Warning
System prevent loss of life from locally generated tsunamis.
ANSWER: Not necessarily. Even if a completely
automated regional system was established in PNG, recipients
of the warning must be prepared to act immediately upon receiving
it, through an established plan of action. PNG, does not have
such plan of action or adequate communications infrastructure
to remote rural areas at the present time. Without such communications
infrastructure in place, without a standard operating plan for
action, and without frequent disaster drills, dissemination of
a tsunami warning through even a regional national center to
a remote rural area close to the earthquake epicenter, would
not do much good. However, with automation and computerized communications,
coupled with preparedness, a warning from a regional center could
be issued within three or so minutes, and could help save the
lives of people further away from the tsunami source.
QUESTION: In the absence of a local warning
system, how else could people be warned?
ANSWER: The earthquake motion itself
is the best warning for the people in a danger area near the
coast. Strong shaking due to the earthquake is the best warning
to run immediately to higher ground or to evacuate vertically.
However, such automatic response to this natural warning must
be part of a program of preparedness and education, particularly
for children. A program of preparedness requires educational
materials drills, and some basic understanding about the tsunami
AFP photo of
QUESTION: What chances do people have
to survive a local tsunami with little or no warning in a flat
on a solidly engineered structure may be the quickest way of
surviving a tsunami in flat area even if there is no warning
other than the natural warning of the ground shaking. In Hawaii
for example, a very developed area with many solid concrete structures
vertical evacuation has been implemented, since it would be impossible
to evacuate thousands of tourists inland Moving them above the
third floor of a hotel which is solidly built assures their safety.
For remote flat areas
such as Papua New Guinea where the recent tsunami occurred, evacuation
to a steel or concrete platforms, erected at least 30 feet or
more above ground and quickly accessible, could have saved many
QUESTION: Why is the area of the Pacific,
especially around Papua New Guinea that much prone to tsunamis?
ANSWER: The area north of Papua New
Guinea bordering the Bismark Sea marks the boundary of very active
tectonic plate interaction, where a disastrous tsunami can be
expected again in the future. It marks the boundary between a
tectonic plate known as the Caroline plate under thrusting (subducting)
the Australian Tectonic plate. Catastrophic tsunamis are caused
by larger earthquakes along such zones of subduction.
QUESTION: How far inland and how high
can Tsunamis of 10 or more meters reach?
ANSWER: Tsunami run-up is the vertical
distance between the maximum height reached by the water on shore
and the mean-sea-level surface. Thus, the height to which a tsunami
will reach will depend on the offshore slope over which the tsunami
travels (as that determines its terminal velocity), the slope
on land and the land topography (trees, buildings, obstacles
which may create friction). Usually a 10 meter tsunami wave near
shore could have a runup height inland which may be much higher
than 10 meters (and even as much as double) because of the topography
and the momentum of greater terminal speed.
TSUNAMI WARNING CENTER ASSESSMENT OF THE 17, JULY 1998 PAPUA
NEW GUINEA EARTHQUAKE. -
THE NEED FOR PREPAREDNESS IN
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