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Geologists arrive to study liquefaction

Published: 10:47PM Friday September 10, 2010 Source: ONE News

A team of American geologists has arrived in Christchurch to study the liquefaction, or sludge, caused by Saturday's quake.

And they say Canterbury's encounter with liquefaction is an event of global significance.

The scientists hope they'll be able to identify areas of potential risk, which could lead to more rigid building codes.

Dr Russell Green, from the Virginia Polytechnic Institute, and Dr Brady Cox from the University of Arkansas, flew in today to study the liquefaction.

"To the average person they say 'wow this is a big mess and it needs to be cleaned up' but we can come in and learn lessons from this," Cox told Close Up's Michael Holland.

The geologists will look at what soil types are prone to liquefying when the pressure of a quake comes to bear.

It's the pressure that causes silty, softer soils to compress, thereby forcing out surrounding water particles - turning the soil from a solid to a liquid.

"Pressure builds up inside and that pressure has to go somewhere and usually it flows up to the ground surface through some cracking," said Cox.

Green says while the liquefaction might seem like a curse to many Cantabrians, for the geologists the event will provide a valuable chance for learning.

"It's something you can't simulate in the laboratory, so when these things happen we have to go out and study it to help future generations benefit from the knowledge we gain," said Green.

Miski Cubrinovski from Canterbury University is also studying the liquefaction.

He's trying to find out what soils are easily liquefiable, and to see if there are ways to predict if liquefaction is going to occur or not.

"From that point of view it is important for us to understand the composition of these soils, what is the depth, what kind of ground conditions exist," he said.

He says soils closer to the sea area are generally more at risk of liquefaction.

Locals also learning fast

Most Cantabrians Close Up spoke to hadn't even heard of liquefaction before the quake.

One homeowner told Close Up she now knew it was "incredibly heavy, and incredibly messy and slimy".

She said she, and others, associated earthquakes with gaping cracks in the ground, not a slimy mess.

Another said she was amazed at the speed at which the liquefaction occurred.

"There were fountains of it, within seconds," she said.