The importance of liquefaction as a principal agent of fatalities and destruction in earthquake disasters has had to be re-considered following two recent earthquakes: 22February 2011 Christchurch earthquake and 28 September 2018 Sulawesi earthquake.
In the former, more than half the damage has been attributed to the consequences of extreme liquefaction, while in the suburbs of Palu, well over half the total fatalities were the consequence of liquefaction-driven low-angle landslides. We now fully appreciate how liquefaction is a separate damage mechanism to earthquake vibration. These examples of extreme liquefaction, flooding streets and ripping buildings apart, demand their own name: ‘ultra-liquefaction’.
This experience opens up a series of research questions. It allows us to go back into historical accounts of earthquakes and find evidence for comparable ultra-liquefaction, swallowing up people and buildings. It also helps us understand how attempts to create earthquake intensity scales struggled to include the impacts of liquefaction. If half of the damage or fatalities can be driven by liquefaction what does that tell us around the priorities in modelling earthquake impacts? Where else can we anticipate comparable disasters and what actions can we take to highlight the risks ultra-liquefaction brings to life and property?
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