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Rights: The University of Waikato
Published 21 July 2007

Alistair Cattanach, a structural engineering consultant from Dunning Thornton-Beca, explains how modelling big earthquakes helped analyse the performance of base isolators. How do scientists know that the new Wellington Hospital will withstand the next big earthquake?


A lot of work a lot of testing, physical tests, and computer modeling software which has been used for non base isolation has been through the rigours of time. We have to try and imagine the likely earthquake that come out of the Wellington fault and one of the risks for this site is the Wiretap fault as well. So through Geological and Nuclear Sciences we selected 7 earthquakes which are very similar to what we think will come out of these faults. And we scaled them to give us our 1,000 year event which is the one where the hospital has to continue operating, and a 2,500 year event which is the extreme event where a hospital still shouldn't slide of its bearings. So we scaled those earthquakes and we ran 7 different ones through in the two different directions, so 14 different analysis we had to do. So we are pretty confident with the approach that we use to understand the physics of something that’s a pretty extreme earthquake event.

Capital & Coast District Health Board
Dunning Thornton Consultants Ltd
Fletcher Construction Company Ltd, The
National Information Service for Earthquake Engineering (NISEE)