I never realized till the Feb 2011 Christchurch earthquake the significance of aquefaction, when earthquakes occur in areas of a certain geological make-up.
What was once ordinary brown soil with grass growing on it, people's lawns, became covered in fine grey silt. Truckloads of silt had to be carried off. This occured not only in the eastern suburbs, on reclaimed land, but also right in the CBD (Central Business District).
I talked to one person from the eastern suburbs, who said after the earthquake water and silt started pouring up out of the ground like. They got in their car for some reason straight after the quake, probably to go and look for a family member. By the time they got to the car, there was water up to their ankles. By the time they had driven the car one block, it had become bogged down in knee-deep grey silty muck.
Many areas were red-zones as not-to-be built on after the quake.
Most of the buildings in the CBD have been demolished by demolition crews, and the area will be entirely rebuilt.
Christchurch was I think built over an old alluvial river delta.
