On behalf of the international tsunami survey team which conducted the PNG
survey last week, I would like to clarify for the entire community the goals
of our field work. I will also try to answer some of the questions raised in
earlier email messages before our departure and after our return, regarding
the necessity of conducting the survey shortly after the event, and the
contributions of these surveys to tsunami hazard mitigation in the local
communities, as well as to the scientific community at large.
In this effort, I have incorporated recent comments from my colleagues de Lange, Gonzalez, Imamura, Okal and Yeh, who have discussed these issues in the tsunami BB or in private messages. I will provide below an index of the issues covered in this lengthy message to facilitate reading and referencing, as many tsunami BB regulars are already very familiar with some of them and they can skip them.
1) The objectives of tsunami field survey.
2) Why the survey has to be conducted immediately after an event.
3) About the International Tsunami Survey Team.
4) The timing of the PNG survey.
5) The contribution of the PNG survey to PNG.
1) The objectives of a tsunami field surveys.
The objective of a tsunami field survey is to identify quantitatively the inundation pattern and determine the runup height distribution along the stricken coastline.
By determining the inundation pattern and modeling the seafloor deformation, the inundation data help better predict what the inundation might be in nearby areas should the same zone rupture in a different location in the future, with a different seismic moment. Through hydrodynamic inversion, the results may help determine if this is the worst-possible event expected in this area and whether the possibility for a transpacific tsunami exists in a future rupture. They may also help explain why an event may appear initially anomalous, in the sense that the tsunami damage reported may be incommensurate with the reported earthquake size. This type of understanding can lead to the production of inundation maps, similar to those in Hawaii, Japan, and currently under development for many mainland Pacific communities in the US. Having access to such inundation maps helps the local authorities locate schools, hospitals, fire-stations and other critical facilities.
2) Why the survey has to be conducted immediately after an event.
The objective of a tsunami survey is to measure inundation or flow depth heights and inland penetration distances, whenever watermarks and other indicators can be found. Most watermarks are highly ephemeral and they maybe lost only after a single storm. Earth-moving equipment may destroy the vegetation the ITST relies upon to infer the direction and size of the tsunami currents. Eyewitnesses usually move to safer areas or they are relocated, and sometimes may not welcome being tracked down months later to discuss what may well have been the most painful experience of their lives. Quite frequently, once an official version of an event circulates, all eyewitnesses report identical information, as it is in human nature for people to trust what they hear or read form the press instead of their own eyes. When this type of information is lost, it becomes much more difficult than already is to reconstruct the event.
All prior surveys were conducted within a two-week period from the event; on two occasions within one week, and once on the following day. The field work unobtrusive. Without a single exception, the ITST members have had the enthusiastic support of the local "lay" people, who always turn out to be very sophisticated, understand immediately that the work benefits them primarily, and ask many interesting and difficult questions that further guide in a substantial fashion the team's work.
When seismologists participate, the survey also involves measuring distributions of aftershocks through portable seismometers that are deployed in strategic locations to complement local networks. The distribution of aftershocks helps determine the rupture area and thus better identify the seismic slip. Clearly, measurements of aftershock distribution has to be done as quickly as possible.
3) About the International Tsunami Survey Team (ITST for short)
In the past six years, the international scientific community has responded to all previous nine major tsunami disasters (Nicaragua, 1992, Flores, 1992, Okushiri, 1993, East Java, 1994, Mindoro, 1994, Kuril islands, Russia 1994, Manzanillo, 1995, Irian Jaya, Indonesia, 1996, Peru, 1996) by dispatching a team of scientists which has come to be known as the International Tsunami Survey Team (ITST for short). More than thirty different colleagues and more than twenty different students have participated in these surveys, from Indonesia, Korea, Japan, Mexico, Peru, the Philippines, Russia, the United Kingdom, and the United States. In the PNG survey, we were joined by colleagues from Australia and New Zealand.
The team has always welcomed all interested colleagues to participate in the survey, as funding allows, and particularly from colleagues who have not been in a tsunami field survey before. No colleague who has had funding to participate and could travel on the dates scheduled has been turned away, and with the exception of the Nicaraguan event, all scientists participants have co-authored publications immediately after the event.
As was discussed in the Esthes Park workshop organized by Jim Lander and Harry Yeh, it would be desirable if internationally recognized bodies such as the IUGG Tsunami Commission or the ICG/ITSU could undertake the timely organization of these surveys after consulting with the local authorities. Unfortunately this has been difficult to do because these bodies do not have yet the resources to commit funds on such a short notice through national funding agencies or through UN/UNESCO/IOC. However, all surveys have been conducted by members of these internationally recognized bodies, and there are few if any of the scientists in these bodies who have not been in the field in at least one survey, and many have been in all of them. So, de facto these surveys are conducted by internationally recognized bodies. Further, no survey has ever been conducted without a prior invitation from an appropriate local authority or without notifying consular authorities.
The question has been raised as to how do ITST scientists communicate their "final" results with the local scientists, after making their preliminary presentations on site. In the past, the surveys have established the basis for closer cooperation between local government agencies, local scientists and the home institutions of ITST team members, and in many cases have helped forged lifelong friendships. As a result of the Indonesia surveys, several Indonesian scientists are doing graduate work in Japan and in New Zealand funded by both Indonesian and international grants. Philippino scientists were invited and participated in at-least two post-Mindoro international scientific meetings where the event was examined at depth. The team visited Nicaragua again three years after the 1992 tsunami and trained three local scientists in field work and in tsunami hazard mitigation. The international community visited Okushiri on the 5th year anniversary of the 1993 tsunami disaster and presented to the mayor and other officials its collective findings about that event. These post-event contacts -of course- depend on initiatives from all sides, but it is clear by the still ongoing studies of all 1992-1996 events continue keeping the international community vigilant in developing better hazard mitigation technology to prevent tidal waves from claiming lives everywhere around the world.
4) The timing of the PNG survey.
Travel in remote areas of PNG is difficult even for adventure travellers under non-emergency conditions. When planning this survey, it was impossible to coordinate the travel of all interested parties to fit everybody's schedule . Field surveys are not package tours, and perhaps the only detail that can be fixed in advance is where and when the team will meet.In this survey, the plan was drawn after meeting with Dr. Letz, of the Geophysical Survey of PNG, in Wewak on August 1 and confirmed after meeting with the disaster relief officials in Aitape on August 2.
As in many earlier surveys, a decision on a tentative start date was made by our Japanese colleagues, sometime on July 19th. On July 20th, US and Japanese scientists communicated and agreed to meet on July 31 in Port Moresby in PNG and then proceed the following day to Wewak and from then to Aitape to meet with the local civil defense authorities.
As in all earlier surveys, one person from Japan and one from the US undertook the communication with appropriate national organizations to request resources for the survey, and with the PNG government authorities to request permission. As before, to minimize the additional work burden of local government officials and local scientists who would otherwise have to respond to multiple requests, the Japanese team coordinator wrote to the local authorities, on behalf of the entire international team. Both the organizers of the Japanese and the US teams wrote to the embassies of the Republic of PNG in Tokyo and Washington to inform them of the team's plans and to request assistance with visas. The US team also wrote to the PNG consular authorities in Australia, who might have been better able to provide information about local conditions; in all our letter we left the possibility open for postponing the survey. The PNG embassy in Tokyo responded first, enthusiastically supporting the effort and generously waiving all visa requirements as well as custom formalities for the survey equipment. The PNG Consulate in Cairns, Australia responded shortly thereafter to the US request, assuring that the ITST would be allowed to travel on visas issued at the first port of entry in PNG.
In addition, the Japanese team's coordinator contacted Dr. Letz of PNG's Geophysical Observatory on or around the 21st of July advising him of ITST's preliminary plans. Dr. Letz's initial response was supportive, and continued to be so throughout the survey's planning. However, the Japanese and the US coordinators agreed with him that the first field team would only attempt an aerial survey, if the local authorities felt that a ground survey would interfere with their relief efforts. To this end, it was decided that the team would have the smallest number of people possible from Japan and the US, to allow greater flexibility for air transport, and so that local scientists could be included, as their schedule permitted. In fact two colleagues from Australia and New Zealand replaced US and Japanese team members who would have otherwise joined the team.
Unfortunately, as in earlier surveys, our schedule could not accommodate everyone who contacted the two team organizers either in Japan or the US. One Australian colleague who was interested in participating could not attend on the planned dates as he had prior commitments; many other colleagues around the world could not commit to come on such short notice and without more knowledge of the specific plan, or without written assurance of funding. Again, these surveys are not package tours, and all participants make nontrivial adjustments to their own lives to travel in remote areas of the globe on short notice. Without exception, all participants have always paid their own expenses, hoping to be reimbursed sometime upon their return, which -for one survey- took place more than six months later. Everyone from Japan the US and elsewhere who had expressed interest in joining this PNG survey was advised that it was unknown if there would be access to the most severely affected area around Sissano, and that depending on this team's findings, there might be a second survey several months later. Everyone was advised that all members were paying their own expenses for the time being.
While in the field, the ITST met with Drs. McCue and Somerville from the Australian Geophysical Survey Organization who had already been in the stricken area for several days working with Dr. Letz deploying seismometers to measure aftershocks. Since the ITST was also deploying seismometers, the two teams coordinated for the optimal location of all available instruments to cover the largest possible area. Had the survey been postponed, the instrument coverage would not have been as extensive as it will be now.
As it turned out, our timing was appropriate, and if anything it came a bit late. While in Aitape at our debriefing meeting with the chiefs of both PNG Government and church relief officials, we were told :
"We were expecting you last week... Where have you been ?... There are wild rumours widely circulating that there will be a second wave exactly fourteen days after the first, and even people in areas not affected are afraid to return to their homes... There are rumours that this was caused by a submarine explosion of unknown origin... There are rumors that this event was caused by the impiety of some people...The local fishermen have been forbidden from fishing in the open ocean because they are afraid of contamination...We need you to help us explain to some superstitious people that this is a natural phenomenon...We need you to tell us where it will be safe to return people to...
(All the above has been recorded on video tape.)
The very day we arrived in Aitape, the field hospital which had been set up in Vanimo by local and Australian doctors was closed, and remaining patients transferred elsewhere. Tragic as the emotional and physical conditions of many injured was, the volunteer New Zealand surgeon who was in Aitape was planning to return back to New Zealand, as there were no more cases which required specialists' help. The emergency situation appeared to be under control and the focus was shifting to transferring patients back in their communities, relocating people and establishing a reliable supply line to the refugee camps. In this regard, the PNG authorities did a remarkably fine job, despite the fact that this was the first tsunami disaster since independence.
Finally, let me write that before the team arrived in PNG, there was some concerns raised by colleagues who have not participated in these surveys before, as to whether our presence there would interfere with local relief efforts. The ITST has a well-established record of working unobtrusively; in fact, in most prior surveys it is the local authorities who are eager to have local scientists work with the team, rather than vice-versa. In an effort not to burden what was already reported as a rather difficult relief effort in Sissano, both the US and the Japanese teams had carried their own drinking water; as it turned out this was useful because bottled water was rationed even in Aitape. The Japanese team had its own dried food, and did not use any of the local food supplies. The US team lived off a small boat, which had carried its food and water from as far east as Lae. Both teams had had cars brought in from Wewak, so that there would be no burden to local transport. The Japanese team and the US team used helicopters, only when otherwise idle; most frequently we flew with the choppers as they flew other missions in and out of the area; with one exception, even as casual passengers, we paid the entire flight cost.
5) The contribution of this PNG survey to the local communities.
The specific contributions of the measurements of inundation data and aftershock distributions will be evaluated by the world community in due course; besides they are only one part of what will undoubtedly end up being one of the most studied tsunami events of the decade. The ITST will send a preliminary report as soon as possible. Here are some of our non-scientific activities, which we hope have been useful.
5a) At the conclusion of the survey, we presented our preliminary findings to the local disaster relief authorities in Aitape. We recommended to them the following
5a1) There should be no relocation of people in locales which are fronted by water and backed by rivers or lagoons. Memorials should be built at the worst stricken locales to remind future inhabitants of this disaster and thus discourage future habitation of high risk locales. These memorials could be as simple as large signs.
5a2) Schools, churches and other critical facilities should never be located closer to 400m from the coastline, and preferrably 800m in at-risk areas.
5a3) There should be evacuation drills annually on the anniversary of this disaster so that all people in at-risk areas know that if they feel the ground moving they should run as far from the beach as possible.
5a4) Every family in an at-risk area should have a designated pine tree with a ladder or carved steps to allow vertical evacuation of the able, when there is no other option.
5a5) The residents in nonaffected areas should return to their homes, after being briefed about what to do in the event that they feel a ground motion or if they see unusual water movements. (As in most other 1992-98 tsunamis, this tsunami was preceded by an LDN, i.e., a leading-depression N-wave.)
5a6) The local pine-tree species withstands the wave attack significantly better than palm trees, and pine-tree forests should be planted in front of coastal communities, whenever possible.
5a7) The local fishermen should be allowed to resume fishing in the open ocean only. The local authorities should collect samples of the lagoon water (as we described to them) and then have them tested monthly to quantify the evolution of the water quality in the lagoon to determine when it would be safe again for fishing and habitation.
5b) Professors Kawata, Okal and myself made four separate presentations in schools and the local hospital, addressing a total of more than 800 people. In our presentations, we explained that tidal waves (the preferred jargon in PNG) are natural phenomena, and that all communities bordering the Pacific Ocean are at risk. (The other team members were working on the field that day, trying to finish the survey.) We described the mechanism of tsunami generation. We discussed some simple warning signs that a tsunami maybe imminent. We stressed that ground motion is not always a precursor, and that anybody who lives close to the coastline should be on the lookout for unusual water motions and they should know what to do. Jose Borrero did a simple physical demonstration to help everybody understand the difference between wind waves and tidal waves. Emile and I answered more than thirty highly-intelligent and pointed questions in these formal meetings, and I am certain that Professor Kawata did likewise in his presentations, which were separate in our attempt to comply with the numerous request we had from missions and schools. Also, while out in the field, we were asked an incredibly larger number questions from survivors about the nature of tsunamis, than the simple questions we were asking, all triggered by their observing our work. As in earlier surveys, and contrary to what some colleagues outside PNG had feared, the survey team was the "show of the day" not vice-versa.
5c) Upon our return to Port Moresby, we made an informal presentation our local scientists colleagues from the Geophysical Observatory and the University of PNG and we discussed at length with them the next step. We provided them with our raw data. In fact, on August 10, the local daily newspaper had an excellent article titled "Fitting the pieces together" written by Professor Hugh Davies of the University of PNG, which provided a great synthesis of the ITST's findings with those of our local colleagues and of AGSO. Numerous stories in the local media (newspaper and radio, we did not have access to a TV) discussed ITST's work and provided journalistic commentary on the team's progress. Our AGSO seismologist colleagues issued a press release upon their return in Australia last Friday, where they incorporated the ITST's findings; this report aired widely in Australia last week. It is clear that the ITST' presence in PNG did help our local colleagues attract the media's attention to tsunami hazard mitigation instead of just to the personal stories, as was appropriate at this stage of the disaster. Interestingly, overall there the only 'quotes' in the local and international papers were from US and Australian scientists outside PNG and not from ITST members, who were for most of the time in the field and unavailable for commentary.
5d) At the conclusion of the POM meeting, the ITST offered to hold a special session in AGU's regular December 98 meeting in California so that all interested colleagues can discuss their preliminary results. Since the AGU meeting is already planned and a massive organization is already in place, a special session was the quickest vehicle for holding an international meeting. This does not preclude another meeting in the South Pacific. Both US and Japanese teams also pledged to seek help to cover the travel expenses of PNG scientists who want to attend, who don't have the time to budget travel funds in their organization in such a short time. This process is currently under way, and we hope that at least one PNG colleague will co-chair the special session.
In closing, I want to thank all other 13 members of the ITST whose names appear below for working twelve hour days, under the most adverse conditions we have ever worked in the 1992-1996 events, well-beyond the call of duty often endangering their lives through exposure to weather, animal and disease hazards.
B. Benson, J. Borrero, J. Borrero, W. De Lange, F. Fujima, F. Imamura, Y. Kawata, M. Matsuyama, Y. Matsutomi, J. Nott, E. Okal, T. Takahashi,Y. Tsuji.
* Costas Emmanuel Synolakis
* Professor of Civil Engineering,
* University of Southern California
* Los Angeles, California 90089-2531
* phone (213) 740-0613
* fax (213) 744-1426