'Black Swans' and Seismic Risk in Megacities of SE Asia​

The 21st century began with a remarkable series of great earthquakes occurring off Sumatra, starting with the 2004 Great Sumatra Earthquake and Indian Ocean Tsunami that caused over 220,00 deaths. While subsequent earthquakes were deadly, none resulted in fatalities on the massive scale of the 2004 event. Can we expect this trend to continue?

 Risk for natural disasters is often expressed with the heuristic equation:

                                Risk = Hazard x Exposure x Vulnerability

This expresses that risk increases with each hazard, exposure and vulnerability, but also shows that risk may increase dramatically if more than one of these factors increase. I will argue in this talk that all three factors have increased markedly in SE Asia since the late 20th century.

Although the hazard itself may not have increased, our perception of the hazard is changing rapidly. Much attention has recently focused on giant earthquakes and tsunamis, but the much smaller 2010 Haiti earthquake was the world’s most deadly. Could such a disaster happen in SE Asia?  I will argue that similar earthquakes pose a potent but largely ignored threat to some megacities in SE Asia – particularly Dakkha, Manila and Jakarta.

Following the 20th century's explosion in global population, SE Asia's population continues to increase at 1% annually, with a median age of 30 and 50% residing in cities. Urbanisation is accelerating, with an urban population of 280 million today that is expected to grow to 373 million by 2030. The chances of a large earthquake directly striking an urban population increase commensurately, and these urban populations are subject to many factors that increase their vulnerability, including: typical residential construction that is non-engineered with poor-quality masonry; many tall buildings that lack adequate earthquake-specific designs; basins of thick, soft sediments that exacerbate ground motions and may be prone to liquefaction.

I will present a combination of  modeling results, compilations of historical accounts and analyses of recent geophysical data that suggest that, although some earthquake-prone areas of SE Asia may currently be in a period of quiescence, the potential for destructive earthquakes is high, and that when such events occur their impacts are likely to be severe.

Phil R. Cummins received his PhD in Geophysics form U. California Berkeley in 1988 and worked as a postdoctoral and research fellow at the Australian National University (ANU) until 1996, when he moved to the Japan Center for Marine-Earth Science and Technology (JAMSTEC). After leading a geodynamics research unit at JAMSTEC, in 2001 he took up a position leading earthquake and tsunami hazard research at Geoscience Australia (GA). In 2011, he accepted a joint appointment between GA and ANU as Prof. Natural Hazards, where he combines teaching and research in natural hazards at ANU with technical application of earthquake and tsunami science at GA.