Tsunami risk bigger than previously thought in parts of New Zealand: report

Parts of New Zealand could be exposed to tsunami that could be 50 percent bigger than previous estimates, government scientists warned Monday.

A report by the government's Institute of Geological and Nuclear Sciences (GNS Science) updated a 2005 report on the country's tsunami hazards, saying earthquakes in some offshore areas could be bigger than previously thought although not more likely.

This was because scientists now had more uncertainty about the maximum size of earthquakes on plate boundaries, the cause of some local and regional tsunamis.

Tsunami generated by nearby offshore ruptures represented a higher threat, while distant tsunamifrom across the Pacific - were a smaller threat than shown in the 2005 report.

Report compiler William Power, of GNS Science, said historical evidence showed that dangerous local or regional tsunami occurred in New Zealand every 40 to 50 years on average.

"So it is likely that at least one such event will occur in the lifetime of most New Zealanders," Power said in a statement.

It was impossible for estimates of size and frequency to be exact, but underplaying the danger would be irresponsible, as it could put people at risk, he said.

The main areas where tsunami posed a greater hazard were around the top and eastern side of the North Island and the far south and southwest of the South Island.

The estimated maximum tsunami wave heights in some of these areas had increased by about 50 percent.

For the most hazardous areas, waves could reach 15 meters above the normal sea level at the shoreline.

The report also pointed out that the estimated tsunami size was lower in some areas that previously estimated.