NZ Herald: Map faults before rebuild – geologist

Isaac Davison writes in the New Zealand Herald about advice from a geologist saying that the faults underlying the Canterbury Plains need to be understood and mapped before the rebuilding of Christchurch begins.

Other unknown faults such as those which caused the Darfield and Christchurch earthquakes could lie under the city, but an ultrasound-like image of the ground beneath Christchurch could be created.

An excerpt: (read in full here)

“The main obstacle to surveys is funding. Dr Quigley said it would be relatively inexpensive – the estimate is $1 million – to undertake geophysical tests under the city.

“Studying aftershocks gave some clues to the potential for faults under Canterbury. But this could be augmented by seismic surveys.

“The combined studies could map a faultline to within 100 metres.

“The most common method of surveying is to use a truck-mounted device, commonly used for oil and gas exploration, which pounds the earth.

“Instruments called geophones are placed alongside the truck’s path, and measure the strength and angle of the vibration when it returns. This data is used to map the earth’s crust.

“Because of the costs and complications of the process, scientists have mostly focused on mapping areas where there is a surface rupture or known activity.

“University of Otago geologist Andrew Gorman said geophysical surveys would be helpful, but were complicated. He said some surveys taken in the Canterbury Plains in September did not provide a convincing image.”