Natural hazards and emergencies

Earthquakes

While earthquakes may occur in Auckland, we are located in one of the lowest earthquake activity parts of New Zealand mainly because of the 300km distance from the Tonga-Kermadec subduction zone.

The Wairoa North Fault is the only identified active fault in Auckland although there is no evidence it has been active within the past 10,000 years. The Kerepehi Fault in the Firth of the Thames is a potential source of damaging earthquake.

Auckland’s strongest ever known quake was the 1891 Waikato Heads earthquake, which had a magnitude of between 5.5 and 6.0. Yet the only damage was some plaster and a chimney in Onehunga falling and some broken pottery and crockery. 


New earthquake reports for Auckland

The Regional Policy and Strategy Committee has endorsed Auckland Council's submission on the government's Earthquake Prone Building Policy.

For more information please read the following reports:

Estimated damage and casualties from earthquakes affecting Auckland (PDF 1.8MB)

Benefits of strengthening earthquake prone buildings in Auckland (PDF 78KB)


Historic earthquakes

The table below lists historic earthquakes felt in Auckland.

Earthquake Date

Location

Magnitude

Shaking felt in Auckland

23 Jan 1855

Wairarapa

8.1-8.2

MM4

18 Oct 1868

Cape Farewell

7.0-7.5

MM4-5

23 Jun 1891

Waikato Heads

5.5-6.0

MM5-6

11 Feb 1893

Nelson

6.6-6.9

MM3-4

6 Oct 1914

East Cape

6.7

MM4

28 Oct 1914

East Cape

6.5

MM3

28 Jun 1921

Hawkes Bay

7.0

MM3

9 Mar 1929

Arthurs Pass

7.1

MM2-3

16 Jun 1929

Buller

7.8

MM3

21 Sep 1931

Bay of Plenty

6.75

MM2-3

20 Jul 1932

Taranaki

6.3

MM2-3

5 Mar 1934

Pahiatua

7.6

MM2-3

15 Mar 1934

Hawkes Bay

6.4

MM3

24 Jun 1942

Wairarapa

7.2

MM2-3

1 Aug 1942

Wairarapa

7.0

MM2

29 Sep 1953

Bay of Plenty

7.2

MM3

18 Oct 1953

Taranaki

5.3

MM3-4

30 Jan 1956

Bay of Plenty 

5.8

MM2-3

23 Jan 1962

Aria

5.5

MM3-4

23 May 1968

Inangahua

7.0-7.1

MM3

11 Feb 1975

Hen and Chickens Islands

4.4

MM3

2 Mar 1987

Edgecumbe

6.1

MM3


Ground shaking in Auckland

Ground shaking is the most common hazard experienced during an earthquake. In New Zealand, earthquake intensity at any specific location is measured by the Modified Mercalli Scale (MM).

MM magnitude

Effects

1

Not felt in general.

2

Felt by a few on top of buildings.

3

Hanging objects may swing slightly.

4

Felt indoors by many, dishes rattle, walls creak.

5

People run outside, crockery dislodged from shelves, hanging pictures move.

6

Felt by everyone, heavy furniture moved, plaster cracks.

7

Frightens everyone, damage to weak buildings, difficult to stand up.

8

General fright and some panic, unreinforced chimneys fall, but only superficial damage to ordinary buildings.

9

Panic is general, some damage to strong buildings, ground cracks, some houses shifted off their foundations.

10

General panic, wooden buildings seriously damaged, landslides, rivers slop over banks.

11

General panic, broad ground cracks, soil slumps, great damage to underground pipes, few buildings remain standing.  

12

General panic, total destruction, objects thrown up in air.

The amount of ground shaking depends on a number of factors including the earthquake size and location. Auckland’s geology and soils vary considerably and will affect the intensity of ground shaking.

Shaking may be more intensive on softer soils such as those on the Manukau lowlands, floodplains running from the Waitakere Ranges and other low-lying floodplains or estuaries. It is likely to be less so on places built on hard bedrock such as much of the central city. 


Liquefaction

Liquefaction requires very specific ground shaking and soil conditions to happen. It occurs when waterlogged sediments experience earthquake shaking of enough intensity to cause the ground to become weak. This can cause heavy structures, such as buildings, to sink and light structures, such as underground pipes and tanks, to rise up to the ground surface. Once the shaking stops, the ground settles which squeezes water out of cracks or holes in the ground to cause flooding.

In Auckland, the geology and ground conditions are generally hard volcanic rock or ancient mud and siltstones, which are not very susceptible to liquefaction.  Localised areas that could be susceptible include reclaimed areas around the Ports of Auckland, floodplains of the Kumeu and Kaipara Rivers and the Manukau lowlands.

GNS Science have assessed Auckland’s urban liquefaction potential and concludes: “We expect neither liquefaction nor earthquake-induced landsliding to have significant impact on buildings in Auckland (a) because of the low levels of the intensities anticipated in future earthquakes and (b) because susceptible ground is uncommon in the built-up area.”


More information

Visit the GeoNet website for the latest information on earthquakes in New Zealand and for general information visit the GNS website.