Tricia, on 23 December 2011 - 09:56 AM, said:
I don't know what the history was there as far as earthquakes prior to this or the September 2010 quake but this seems to be a pretty active fault now.
Just glad there are only minor injuries reported this time.
Vapor Trails, on 23 December 2011 - 02:48 PM, said:
Well, New Zealand is
in the Pacific Ring of Fire, I'm sorry to say.
Part of the problem is that Christchurch is sitting right on top of a fault...and this was not known until recently; if I understand correctly, it was only discovered in the aftermath of the 2010 quake.
That info is from a Feb 2011 article on the earlier quake
from The Guardian.
Just in case anyone wonders what the term "liquefaction" means--it's referred to briefly in the article from the New Zealand Herald that Vapor Trails gave the link for---the earlier article also has a pretty clear explanation for the layperson.
John Clague, an expert in natural hazards at Simon Fraser University in British Columbia, said it was unclear what caused such serious damage to modern buildings, but said the answer could be the "liquefaction" of the ground when the shaking began.
"Liquefaction is a huge problem in Christchurch because the city is built on an alluvial plain, on sediments that are vulnerable to liquefaction," Clague said. "When shaken, these sediments transform into a liquid, causing irregular settlement of the ground, which is extremely damaging to buildings and buried structures, like water lines."
So yes...those poor folks. An historic and I understand beautiful city, more vulnerable than anyone had dreamed.