A hazardous week around the country

A hazardous week around the country

Natural hazards hit New Zealand with a vengeance last week, with an earthquake, a tsunami, floods, large waves, and gales all making their presence felt.

The notable hazards included:

* On Friday 22 August a magnitude 7.1 earthquake – the fifth biggest earthquake in the world this year – struck Fiordland. It occurred at 12.12 a.m., about 70 km northwest of Te Anau, and triggered more than 200 landslides in Fiordland National Park. Dozens of aftershocks have been recorded, some of them sizable earthquakes in their own right, including 19 aftershocks greater than magnitude 5 and one greater than magnitude 6.

* The Fiordland earthquake also triggered a small tsunami. The series of two main waves moved up the West Coast, reaching the Jackson Bay sea-level recorder (260 km north) just after 2 a.m. on Friday, 22 August. Although the tsunami was small – reaching a maximum height of 0.3 m – it emphasises how vulnerable New Zealand is to ‘local’ tsunami and not just the better-known ‘remote’ tsunami from across the Pacific.

* A low depression off eastern Northland caused a flurry of wave activity on Wednesday, 20 August, with gale force winds of up to 65 knots buffeting the area. The Auckland Regional Council’s wave buoy at Mokohinau Island (north of Great Barrier Island) recorded wave heights of between 6 and 11 m. High waves generated by a series of mid-Tasman lows over the past few weeks have continued to erode some sandy shorelines along the north-east coast.

* Whitianga in the Coromandel and Palliser Bay region in southern Wairarapa both got a drenching. In Whitianga 109 mm of rain fell for the 24 hours up to 2 a.m. on 21 August, and continuous heavy rainfall saw Palliser record 105 mm for the 24 hours up to 2 a.m. on 22 August – that amount of rainfall is expected only once in every 10 years.

So, was this hazardous week exceptional? Not according to National Hazards Centre Coordinator Dr Warren Gray. “It’s winter, so we are going to get those low weather systems. It just happens that we got a major quake at the same time.”

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