AFTER THE TSUNAMI – HARNESSING AUSTRALIAN EXPERTISE FOR RECOVERY
Canberra, 31 March 2005
Follow-up group reports and case studies
Group 1: Warning and preparedness
Warning falls into 3 clear categories:
- The issuing of a tsunami forecast
- Disseminating the tsunami warning/forecast to the coastal communities
- Ensuring that the public are aware of what action needs to be taken. This has two parts
- When a warning is received regarding a regional tsunami
- When an earthquake is felt which might have induced a local tsunami.
Preparedness relates to actions which can be undertaken to mitigate the effects of a tsunami and include:
- Identifying the tsunami risk
- Taking steps to mitigate those risks.
Issuing a tsunami forecast
Ideally a tsunami warning would include a forecast of the likely size and impact for each affected coastal community. There are a number of steps in going from an earthquake to an impact forecast:
- obtain an earthquake solution (location, mechanism and magnitude);
- estimate the tsunami arrival times and potential impacts;
- verify the tsunami from ocean height data;
- calculate a tsunami model incorporating seismic and ocean height data;
- produce an impact forecast, incorporating the refined tsunami model, coastal bathymetry, topography, infrastructure and population.
Each of these five steps requires significant scientific expertise including, seismic network design, seismic network operations, real-time processing, sea-level network design, deep and shallow water tsunami modeling, and run-up and impact modeling. The current best practice for the last 2 steps is to pre-compute the models and have a database of model scenarios, which in real-time are chosen based on the seismic and sea-level data. Step four gives the expected wave height, with the shoaling effect taken into account, at various locations along a coast and step five the likely impact on people and infrastructure of that tsunami. To achieve step 5 you are in effect doing a comprehensive tsunami risk assessment of the coast and storing the models. False warnings are a major problem in that they cause unnecessary distress and people soon begin to ignore the warnings. Having a comprehensive system which incorporates steps 4 and 5 above will minimise the number of false warnings and maximise the ability to assure people that a damaging tsunami is not imminent. Australia has world class expertise in all of the sciences discussed above.
Disseminating the warning
Ensuring that the warning and relevant tsunami forecast is received by all relevant coastal communities is a vital part of a tsunami early warning system (TEWS). In Australia there exists a sophisticated communication infrastructure, which is used to issues warnings of severe weather and storms. The system issues warnings to all sectors involved in emergency management, from state government, to local volunteer search and rescue organisations. The communication infrastructure includes telephone, facsimile, email, SMS, internet and broadcast systems using HF and VHF radio, with the media having a key role. Australia also has well developed systems for disseminating information about less sudden impact events such as fire and flood. These systems have been built up over several decades, with many lessons learnt. To implement a warning system which takes a warning and disseminates it to everybody in every coastal community that will still be operational in several decades time is not a trivial undertaking. Australia has significant expertise in the appropriateness of different message dissemination techniques for different types of communities, which might be of value to other Indian Ocean countries.
Public awareness
As tsunami are infrequent events, despite the current very high level of public awareness in all Indian Ocean countries, long-term public awareness programs are an essential component of a TEWS. In many Indian Ocean countries, including Australia, the most at risk communities are isolated coastal communities and high density coastal settlements. Often these communities have a lower level of technology than the major urban centres. Ensuring that long-term public awareness programs, particularly in these communities, are in place is essential if lives are to be saved when a future tsunami impacts the region. Any education program needs to incorporate basic tsunami information, the difference between local and regional tsunami, what community preparedness is needed and what to do when a tsunami warning is received.
Local tsunami, where the tsunami travel time is less than 30-60 minutes from the source earthquake (eg the 1998 Aitape tsunami in PNG), pose a different problem. No warning from a central authority is possible except where the most sophisticated technology is available (eg Japan). In communities which are at risk from locally generated tsunami an additional level of public awareness is required to ensure the community knows what a potentially tsunami-genic earthquake feels like and to know not to wait for an official warning. Equally important is for people to know what a non-tsunami-genic earthquake feels like, as these earthquakes cause significant distress to people who are shaken by them. Australia has significant experience in public education programs, producing scientific education kits for school children of all ages, science communication in general and producing information appropriate for different cultures. These skills could be of use to other Indian Ocean countries.
Preparedness
Preparedness involves identifying the level of risk and implementing a risk mitigation strategy. Much of the work involved in producing the value added forecasts which include wave height, inundation and impact requires a tsunami risk assessment to be undertaken. This gives each community the information they need to determine what mitigation strategies are appropriate for their community. Risk mitigation can take a wide range of activities from simple tasks such as, identifying tsunami evacuation points, building and maintaining paths to these, and ensuring emergency supplies are stored out of range of a tsunami, through to tasks such as building tsunami proof houses, building tsunami shelters, and major changes to town design to have key infrastructure out of a tsunami’s range. The most appropriate mitigation action will depend on each community’s specific situation. For example a low lying coastal community with no hills nearby will need a different strategy to a community with easily accessible hills. The other key aspect of preparedness is having highly skilled emergency management agencies. Rapid and effective response by emergency management agencies is vital in minimising loss of life and suffering of the survivors. This requires significant training and infrastructure well in advance of a disaster. Australia has well developed systems of emergency management at the local, regional and national level. Again the substantial skills Australia has in risk assessment, risk mitigation and emergency management could be of value to other Indian Ocean countries.
Anecdote
This was widely reported in the weeks following the tsunami of December 26. This version is from the Association of American Geographers Newsletter.
In one of the more hopeful tales from the recent tsunami disaster, a young British girl credited school geography lessons with her ability to recognize the impending tsunami and warn her family and other beachgoers in time to avoid the onslaught of the waves. The Associated Press reported in a story on January 1, 2005, that ten-year-old Tilly Smith from Surrey in England, was vacationing with her family on Maikhao beach in Phuket, Thailand, when the tide suddenly went out. Remembering a recent lesson on earthquakes and tsunamis from her geography teacher, Andrew Kearney, at Oxshott’s Danes Hill Prep School, Tilly warned her mother about the danger. Her parents informed other beachgoers and staff at their hotel, which was quickly evacuated. The wave crashed a few minutes later, but no one on the beach was killed or seriously injured.