Tsunami Hazard to Coastal Populations

USGS: Map of very recent Earthquakes in the Australian region and current tsunami warnings for the Pacific Ocean - both US sites. Historical Australian earthquakes.

Reduce your personal risk - May 2008

Be alert and prepared - not alarmed. This is a low-probability, high-consequence event that calls for a little preparation in case a warning is issued. These are similar to the things that people in tropical locations do to prepare for cyclone warnings.

Although the likelihood of a mega-tsunami is low there are some simple things you can do to significantly reduce the risk:

Identify if you live, work or play in a vulnerable location - find out the approximate height above mean sea level. As a rough guide coastal and estuary land less than 10 metres above mean sea level is "at risk" and 5m or less should be considered "vulnerable". Google Maps has a sea level rise add-on that can give a very rough guide (detailed modelling is needed to assess vulnerability as there are many factors that influence tsunami inundation). The following links are to JPG screen snapshots from Google Maps - red shows 5m contour and yellow shows 10m contour - be prepared for a shock: - Narrabeen, Manly, Sydney , Brisbane, Gold Coast, Sunshine Coast, Nowra, Wollongong, Gosford, Newcastle and Forster.
Identify a safe location to go to in the event of a tsunami warning - a nearby hill or headland or at least the third storey of a reinforced concrete building
Plan an evacuation route to reach that safe location (avoid the need for driving a car because the roads will likely gridlock)
Subscribe to the email or RSS warning service of the US Pacific Tsunami Warning Center
Consider subscribing to a mobile phone alert service like the Tsunami Institute in Germany or Tsunami SMS (expect about 5 warnings a month for the Pacific Ocean and maybe one per year relevant to your location)
If you receive a tsunami warning that is relevant to your location, or feel an earthquake, quickly get your evacuation plan into action. If a mega-tsunami does inundate the area do not return to low-lying land for at least 2 hours as other waves are likely to follow after the first wave and each wave can last for 20 to 30 minutes.
Approach your local council and ask them to develop a tsunami warning action plan and infrastructure (such as a public address system) and to have inundation modelling carried out.
Most importantly, relax and enjoy living near the ocean, knowing that you have made basic preparations for a worst case scenario

Update March 2008

DRAFT presentation on the hazard to Sydney - including recent computer modelling of a mega-tsunami from the Tongan Trench that has similar features to the 2004 Indian Ocean Tsunami.

12Mb Quicktime presentation
3Mb PDF of the presentation
Notes for simulation of an Magnitude 9 earthquake at the Tonga Trench by Charles Mader (from the DVD with his book Numerical Modeling of Water Waves). The chances of such an extraordinary but deadly event are unknown at this stage (however, a magnitude 7.9 earthquake occurred in 2006 and a Magnitude 8.1 occurred south of New Zealand 3 days before the 2004 Indian Ocean event). The Mader modelling was based on the actual tectonic movements for the Sumartran earthquake that caused the 2004 Indian Ocean tsunami (Aug08: assumption independently confirmed). Others have noted that the Tongan Trench is the fastest known subduction zone. The resulting tsunami is particularly devastating for the East Coast of Australia, with a predicted height of around 10m (the deep water wave height would be less than that modelled due to dispersion but the shallow water amplification would counteract this effect meaning a likely 10m runup along many coastlines). It has been estimated that 330,000 people live within the 10m elevation zone along the coast (and many estuaries) of New South Wales. Adding the Queensland Coast the population at risk is likely around half a million - something that deserves urgent attention (even if an M9 Tongan earthquake is a one-in-10,000 year event, which seems very conservative, this would mean an equivalent annual death toll of 50).
Reducing The Death Toll From Tsunami (written a fortnight after the Indian Ocean disaster)
Snapshot from Google Earth (500K GIF) showing recent earthquakes and plate boundaries in the South Pacific.
June 2008: Apparently Geoscience Australia has been undertaking similar simulations to the Mader work but I have not come across any published results (update: see next item).
15 Aug 08 Breakthrough! Illawara Mercury: Tsunami a real threat to Illawarra: professor - a tsunami education and evacuation plan for Illawarra would be released in November.

The Joint Australian Tsunami Warning Centre - Opinion: the "alert" side of things is progressing well. The "response" and "preparedness" aspects are not so good!

May 08: This report reaches a similar conclusion - Taking a punch: Building a more resilient Australia - report "We need greater clarity on the precise management and coordination arrangements in the case, for example, of a devastating tsunami impacting on southeast Australia...The Commonwealth agency seen to be responsible for this, Emergency Management Australia (EMA), has no mandate, legislation or Cabinet endorsement with which to take command. The delivery of EMA functions for the most part is the result of goodwill on behalf of other agencies. This is clearly not a satisfactory situation." "A $70 million early warning system is being set up to record any earthquakes that could trigger giant waves to strike the NSW coast but it’s not clear how communities get informed, particularly if a night-time incident occurred..."

Update July 2006 (see also Australian news)

Emergency Management Australia is working on an "Australian Tsunami Warning System" - good news and hopefully we will soon see the implementation of civil warning systems for Sydney coastlines.

Key points (thanks Mark Sullivan, Director Capability Development EMA):

EMA is working with States and Territories and relevant industry, education, volunteer and community sectors to enhance community preparedness through awareness raising, education and training.
Over four years, from July 2005 to June 2009, the Bureau of Meteorology, Geoscience Australia (GA) and Emergency Management Australia (EMA) will implement a comprehensive end-to-end Australian Tsunami Warning System (ATWS). The ATWS will be delivered through enhancements to the existing Australian Tsunami Alert Service (ATAS), and will comprise upgraded seismic and sea level monitoring networks, computer modelling of tsunami propagation to aid impact forecasting, and national awareness raising and capacity building initiatives. The ATWS, once fully operational, will deliver timely and accurate warnings to the Australian community in such a way as to elicit an appropriate response from those at risk.
By 2007 estimates will have been made of the credible limit of offshore tsunami wave height for the entire Australian coastline.
Inundation modelling is being undertaken for some West Australian coastal communities
Australian Emergency Management Committee's Tsunami Working Group will meet in September 2006 with a view to agreeing on a national strategy for awareness raising and capacity building. Some local jurisdictions have already developed hazard specific arrangements for tsunami, and EMA is committed to working with all jurisdictions to enhance these already existing arrangements to effectively respond to a rapid onset event such as tsunami, including the eduction sector.
Communities and key stakeholders have been, and continue to be, engaged; and a national picture of tsunami risk is being developed. In the very near future, the Australian community can expect to be provided greater access to relevant
awareness material, and those with key responsibilities will further benefit from tailored education, training and exercising. On this basis, the Australian community will come ever closer to being a 'Tsunami Aware Community', and thus be better prepared to respond appropriately to signs of tsunami in Australia and overseas, as well as respond in a timely and appropriate way to ATWS warnings.

Australian Emergency Manuals
Australian Journal of Emergency Management:

Observations on Tsunami disaster in Papua New Guinea - 1998
After the Wave: A wake up warning for Australian coastal locations King and Gurtner consider Australia’s vulnerability to tsunamis and storm surges...The increasing emphasis on disaster reduction through mitigation
and preparedness has put greater responsibility on local government and relevant authorities to ensure
that such lessons are understood and used to mitigate future contingencies. The tsunami is a warning that
reinforces current mitigation efforts, and in particular, the long-term goals of education and the planning
of coastal land use.