'No big quakes for 7000 years'

People living on the North Island's east coast need not stress too much about earthquakes for the next few thousand years, GNS scientist Rob Langridge says.

According to him, that's because the land itself has relieved its stresses through a series of large earthquakes and is now going through a relatively quiet period before the stress builds up again.

Dr Langridge, who has studied the history of earthquakes in New Zealand, presented some of his findings at a Royal Society lecture in Napier on Thursday, as part of Art Deco Weekend.

The devastating Hawke's Bay earthquake of 1931 - which led to central Napier being rebuilt in art deco style - was caused by a faultline that moved once every 7000 years, he said yesterday. "That was magnitude 7.8, one of New Zealand's largest on-land earthquakes and certainly the most devastating as 256 people lost their lives."

Since European settlement there had been a series of large earthquakes from northeast Marlborough, through the Wairarapa and Hawke's Bay, up to Wairoa.

"These included the 1855 Wairarapa earthquake, magnitude 8.2; and the 1863 Waipukurau earthquake, which we estimate at magnitude 7.5." Others in the series were at Wairoa in 1932, Pahiatua in 1934 and Masterton in 1942.

"Since then things have been fairly quiet," Dr Langridge said.

He expected this to continue because his research showed that movements in the Napier fault line, and others to the south, had happened at large intervals.

 

Recent earthquakes in Fiordland indicated that New Zealand's next big shake could come in that region, Dr Langridge said.

 

The Dominion Post