6 Aug 2013

Dam to withstand 'most powerful tremors'

9:41 am on 6 August 2013

The Hawke's Bay Regional Council says it has not researched whether its proposed Ruataniwha Dam is likely to trigger earthquakes, but it will be designed to withstand the most powerful tremors.

The proposed dam site is traversed by several active fault-lines close to the Ruahine Ranges.

A Columbia University research professor, Leonardo Seeber, says dams the size of the Ruataniwha project can trigger earthquakes through Reservoir Induced Seismicity (RIS) in which the weight of the water stresses fault lines.

He also says having a dam wall about 100 metres high could also be a factor in inducing quakes.

The Ruataniwaha dam will have an 82-metre-high wall, and Professor Seeber says that's high enough to justify modelling work to see what the dam's seismic effects might be, but the regional council says it hasn't identified a need for RIS modelling.

Its investment company, which is running the water storage project, says several existing dams with similar size and located close to faults have not induced measurable seismic activity at ground surface level.

It says the dam and associated structures are designed for what is called the Maximum Design Earthquake.

That means in a massive earthquake, the dam may be damaged but will not breach.