New Zealand, the ‘Shaky Isles,’ dreads ‘Big One’

By David Barber

WELLINGTON, New Zealand – With seismologists recording up to 15,000 earthquakes a year, New Zealand deserves its reputation as the “Shaky Isles,” but most are too small to be felt by the country’s 4.3 million people.

Up to 150, however, are large enough to register, and every school child is drilled on how to react to an earthquake – get under your desk or in a doorway when you feel a tremor – and taught the need to prepare for the “Big One.”

Although they grow up to be aware of living in one of the world’s most quake-prone countries, all do not necessarily heed the lesson by keeping survival packs and emergency supplies in their homes and workplaces.

Civil defense officials, who often despair of their warnings being taken seriously, hope the magnitude-7.1 quake that devastated much of the South Island’s largest city, Christchurch, on Saturday – a once-in-a-decade event – would come as a pertinent reminder.

It should because, although it was centered just outside Christchurch, it was felt over more than 1,200 kilometers of the country, which runs 1,600 kilometers from the bottom of its South Island to the top of its North Island.

In terms of extensive damage, it was the worst quake to hit New Zealand since a magnitude-7.8 shake destroyed most of the North Island city of Napier in 1931. That tremor killed 286 people, but Christchurch was saved from similar carnage because Saturday’s quake struck at 4:35 am (1635 GMT Friday) as the city slept.

Being centered in an area seismologists had not identified as quake-prone, it showed that nowhere in the country is safe from a devastating tremor.

The epicenter of Saturday’s quake was 100 kilometers from the Alpine Fault, which runs about 600 kilometers up the spine of the South Island and is the boundary of two massive geological plates that are constantly grinding against each other.

Seismologists said it has ruptured four times in the past 900 years, each time producing an earthquake of about magnitude 8, lifting the Southern Alps in the process and producing some of New Zealand’s most spectacular scenery.
It last erupted in 1717, and scientists predicted a “high probability” that it would produce one of the biggest earthquakes since Europeans settled in New Zealand in the mid-19th century within the next 40 years.

The capital, Wellington, which has five major fault lines, has long been regarded as the most likely to experience the Big One.

Seismologists said the so-called Wellington fault, which last produced a quake of about magnitude 7.6 between 300 and 500 years ago, would spawn another inside the next 200 years.

As 20 aftershocks ranging from 3.9 to 5.2 on the Richter scale were recorded in about 15 hours after the early-morning shock, they said it is impossible to predict whether another Big One would hit Christchurch.

But records showed that Napier was struck by a massive aftershock measuring 7.3 10 days after the city was leveled 89 years ago.