The Breakroom > The Water Cooler

New Zealand Earthquake

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saw:
I feel very sorry for all of the people in New Zealand.  :(

Pete49:
John I have a question about the quake. I know its probably known but I have no idea what the grey silt that they are shovelling away is or how it is connected with the quake.
Other than that I was shocked at the loss of life there and my heart goes out to those that have lost loved ones.
Pete

Stilldrillin:
Pete.
As I understand it......

Christchurch is built on a layer of gravel, with water seeped down through.

An earthquake forces the water up through the gravel to the surface, making everything "float", and bringing the fine particles with it.

David D

John Hill:

--- Quote from: Pete49 on February 25, 2011, 07:39:14 AM ---John I have a question about the quake. I know its probably known but I have no idea what the grey silt that they are shovelling away is or how it is connected with the quake.
Other than that I was shocked at the loss of life there and my heart goes out to those that have lost loved ones.
Pete

--- End quote ---

Yes, as David said much of the city was built on reclaimed wet lands and the shake causes the light stuff to come to the surface while the heavier gravels, road foundations, building foundations and even buildings and vehicles tend to sink right in.   In some parts of Christchurch if you try to dig a post hole it will be full of water before you have got the post in as the water table is very close to the surface.  They have artesian water in some areas too so obviously any disruption to the ground can allow that water to rush to the surface.   The 25 storey hotel that has a dangerous lean in down Christchurch has presumably lost its foundations, but thats just my summation I have not seen any official comment on that detail. 

We are 80kms south built on a gravel and sand alluvial plane but the water table is much lower being 200' or so down and liquifaction is not an issue here, well thats what I tell myself anyway! ::)

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