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Equipment to shed light on city's tiny tremors

By Craig Borley

When the All Blacks score a try at Eden Park, the earth moves.

Or at least that's the theory, one that will be tested by monitoring equipment buried 250m below the new south stand.

Drilling on the seismic monitoring project began yesterday, and is expected to reach the target depth within three weeks.

By early October it is hoped measurements will begin being sent from the hole to the Auckland University scientists and engineers behind the project.

But while the impact of large crowds on the earth below them is one measurement to be gleaned from the project, its primary purpose is to measure Auckland's frequent miniature earthquakes.

Deep below the city hundreds of small tremors occur each year, but current monitoring systems are unable to record them accurately, Auckland University civil engineering lecturer Quincy Ma told the Herald yesterday.

Mr Ma said the the Borehole Instrument Centre for Eden Park (Bicep) project aimed to record those tremors while being unaffected by the surface "noise" generated by a working city. Surface-based measuring instruments seldom distinguished tiny tremors from normal city activities, such as heavy traffic, he said.

Measuring instruments would be installed at different depths down the hole, allowing a three-dimensional look at soil and rock movement. Scientists at the university's Institute of Earth Science and Engineering would collect and analyse the data.

The knowledge gained from those measurements could allow better understanding of the effects the tremors have on Auckland's buildings, Mr Ma said, and could help in planning future buildings in the city.

The data could also be used to help the planning of future sporting stadiums, to ensure any earth movements they created during events did not affect nearby structures.

Project head Liam Wotherspoon said it was hoped the hole would be the first of many in Auckland - if funding allowed.

- NZ Herald

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