Man-made quake shakes Christchurch
New Zealand's Earthquake Commission has tested structural systems that would stabilise the soil to stop the liquefaction that can cause so much damage to buildings during an earthquake. They set off a a fake quake in a Christchurch suburb, abandoned after the devastating 2011 disaster, by packing the earth with 400kg of gelignite and blowing it up.
The commission tested four foundation types – mixing soil with cement; using a grid of stone pillars; an underground concrete perimeter wall; and soil compaction.
The methods appeared to work. The liquefaction that was produced after the explosions seemed less intense than without the stabilisation system. The columns confined the effects of liquefaction, and the denser ground meant the houses appeared to be stable on the earth.
The final results are still being internationally peer reviewed but the methods have already been transferred to a pilot program for landowners who have been stuck in limbo. Both insurers and builders have been reluctant to risk rebuilding on unstable land. For some, these techniques should change that.