Every few years, tragedies on coastlines around the world remind us of the risk that we face from tsunamis. The 2011 Tōhoku Earthquake and Tsunami demonstrated just how vulnerable we are, and that research is required to better understand the risks we face.
With help from the National Computational Infrastructure (NCI), Geoscience Australia (GA) has recently developed a Global Probabilistic Tsunami Hazard Assessment (PTHA) in collaboration with an international team of tsunami hazard scientists. This is a computer model that simulates thousands of different earthquake-generated tsunami scenarios around the world. It covers most of the world's coastline, giving vital information about which countries and regions are at risk from tsunamis.
The PTHA model considers thousands of different earthquake-generated tsunami scenarios and their probabilities of occurring. Statistical analysis of the suite of scenarios allows estimation of the likelihood of a tsunami of a particular height hitting the coast anywhere in the world. With this kind of information, tsunami hazard scientists can look further into the high-risk areas and do more detailed modelling to support national and local scale risk reduction measures. The work is also useful to global institutions such as the United Nations Office for Disaster Risk Reduction, which needs consistent global analyses to help understand the global-scale exposure of nations to natural hazards and prioritise risk reduction efforts.
Dr Gareth Davies, a hydrodynamic modeller from GA involved in producing the PTHA, says, "This model gives us a global picture of tsunami hazard, something that we have never had before. With a better understanding of the global distribution of tsunami hazards, we can prioritise regions for further high-resolution studies, and ultimately, contribute to tsunami risk reduction measures which reduce the impacts of tsunamis on society."
Because the model needs to be run thousands of times to make the statistics robust enough, each time with slightly different parameters, the computing power required is beyond any standard desktop computer. Instead, to simulate the approximately 20000 scenarios that make up the PTHA, GA uses NCI to do the equivalent of 2500 days of computing, all over the span of a few days. By using many processors simultaneously on NCI's systems, GA can produce all the data they need to put together their rigorous hazard assessment.
Davies says, "This global PTHA could not be run without access to NCI's infrastructure. The high-performance computing systems make it possible for us to run complex algorithms at a global scale. The data we've produced here is already being used to help guide our future tsunami work."
The data output from the PTHA is a combination of tsunami wave run-up height and earthquake frequency estimates, which together give an estimate of the likelihood and potential impact of a tsunami hitting the coast at any one time. That picture of tsunami hazard produced by the PTHA helps identify where higher-resolution localised studies would be most helpful. These can then help governments and planning authorities with important decisions about how best to develop or secure coastal areas.
The partnership between Geoscience Australia and NCI is what enables innovative and impactful research outcomes. By connecting researchers with the advanced computing infrastructure that they need, we make possible previous unimaginable findings.