Since the Canterbury earthquake, we have been fielding a few calls about liquefaction in our region. There have been a few good articles in local papers, but here is a small excerpt from our Risk and Responsibilities Report (the lifelines report).
'Liquefaction is the loss of strength of unconsolidated materials during shaking, with the expulsion of water. Heavy objects such as tanks may sink, list, or float if liquefaction of their foundation or surrounding materials occurs. Sandy layers, up to several metres below the ground may liquefy provided there is sufficient confining pressure, and may cause sand/water fountaining at the ground surface. Liquefaction is commonly responsible for lateral spreading along riverbanks. Unconsolidated, water saturated sandy material is a prerequisite for liquefaction, so areas prone to this hazard tend to coincide with those prone to amplification of shaking and settlement.'
In our region, it is the west coast strip that is most susceptible to liquefaction. The diagram also shows known earthquake faults.
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