Anatolian tectonic plate, north anatolian fault, historical earthquakes Greece, Attica, Earthquakes, Tsunami, , Hurricanes, Volcanic Eruptions and other Natural and Man-Made Hazards and Disasters - by Dr. George Pararas Carayannis

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FREQUENTLY ASKED QUESTIONS ABOUT THE PNG TSUNAMI OF 17 JULY 1998

George Pararas-Carayannis

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 earthquake.

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 hazard itself.

AFP photo of Sissano Lagoon

QUESTION: What chances do people have to survive a local tsunami with little or no warning in a flat coastal area?

Vertical evacuation 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 lives.

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.

PACIFIC TSUNAMI WARNING CENTER ASSESSMENT OF THE 17, JULY 1998 PAPUA NEW GUINEA EARTHQUAKE. - THE NEED FOR PREPAREDNESS IN PNG


 

 

 

 

 

 

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