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New instruments to record earthquakes - 22/04/1999

Scientists plan to install 25 new state-of-the-art earthquake recording instruments throughout the country over the next three months to improve the quality of information recorded during an earthquake.

The upgrade has been funded through a grant from the Earthquake Commission.

The American-made instruments, worth about $10,000 each, have been bought by the Institute of Geological & Nuclear Sciences Limited to boost its nationwide network of 310 instruments that record ground acceleration during a large earthquake.

Two thirds of the instruments will replace older instruments, with the balance being sited at new locations, network manager and earthquake engineer Jim Cousins said.

The new instruments are more accurate and more robust than those they are replacing. They also send ready-to-use digital information to scientists about earthquake ground-shaking immediately and automatically.

" These instruments are built to record accelerations up to twice the pull of gravity. In motoring terms, that’s equivalent to accelerating from 0 to 100km/h in 1.4 seconds," Dr Cousins said.

" They have to be robust enough to function perfectly while the building or structure they are attached to is in considerable distress.’’

If electricity is cut during a big earthquake, the instruments have a battery that allows them to continue sending information on aftershocks for four days after the main shock.

About half of the instruments in the network are bolted to the ground. The rest are attached to buildings, hydro-dams, bridges, and other structures so scientists and engineers can find out how the structures perform during big earthquakes.

Called accelerographs, their functions include:

  • Supplying information that leads to improvements in building codes and earthquake resistant design
  • Providing immediate information about the strength of earthquake ground-shaking to optimise the activities of emergency response teams.

Nine will be located in the Wellington region, five in Christchurch, four on the South Island’s Alpine Fault, and one in Dunedin. Others will be sited at the top of the South Island and in central North Island.

New Zealand has about 200 known active faults and many towns and cities are located within 5km of an active fault. The Institute has concentrated some of its instruments near the most active and potentially destructive faults, while other sites have been chosen to record variations in ground-shaking on different types of ground.

Jim Cousins
Earthquake Engineer
Institute of Geological & Nuclear Sciences Limited

John Callan
Communications Co-ordinator
Institute of Geological & Nuclear Sciences Limited