Hawke’s Bay is one of the most seismically active regions in New Zealand. Getting ready before an earthquake strikes will reduce the damage to your home and business, and help you to survive. Find out about the risks in Hawke’s Bay, and what happened in past earthquakes.
Earthquakes happen without warning. Smaller earthquakes are happening all the time – you can check on these earthquakes at Geonet – but a large earthquake can be frightening and damaging.
However, there is a lot you can do to prepare for a large earthquake and be sure you can cope better with the impacts on you and those you care for.
There is an email sometimes circulated by a self-professed ‘rescue expert’ giving earthquake advice contradictory to what Civil Defence Emergency Management and the New Zealand Earthquake Engineering Society recommends.
Although discredited, the advice continues to resurface, causing confusion about what to do that could result in people getting seriously injured or killed in an earthquake. If you want to know more about why the ‘Triangle of life’ is not good advice, visit the USA Red Cross website.
Research from the United States, Taiwan, Japan and Christchurch (all places with modern, earthquake-resistant building design codes), supports and recommends the core message for New Zealand: Drop, Cover and Hold is the right action to take in an earthquake.
Hawke’s Bay is one of the most seismically active regions of New Zealand! You can find out about current earthquakes at Geonet.
Hawke’s Bay is located on the Australian Plate, about 150 km west of the Hikurangi Trough that marks the subduction boundary between the Pacific and Australian Plates. The Pacific Plate is plunging beneath the Australian Plate at about 42 mm/year.
In the 160 years since substantial written records began, there have been several large and damaging earthquakes. The 1931 earthquake is the one that has remained prominent in our living memory. It was measured at magnitude 7.8 with shaking intensity of MM 7-9 and changed our landscape, the cities and lives.
Hawke’s Bay experiences many smaller earthquakes each year, but another large earthquake can occur at any time and scientists have estimated what earthquakes we might experience in the future.
Our risks include earthquake prone buildings which have been identified within our main cities and towns. Residential dwellings are considered a low risk, but damage may be widespread and require people to be rehoused. Infrastructure networks such as electricity, roads, and bridges and our future social and economic wellbeing are also at risk.
Over the years the damage has been in the millions of dollars – the 2008 Hastings earthquake alone resulted in over a million dollars of residential claims to EQC.
|Shaking intensity (using the Modified Mercalli Intensity Scale - MM)||Description||Estimated Return Period by years|
Hawke’s Bay is located on the Australian Plate, about 150 km west of the Hikurangi Trough that marks the subduction boundary between the Pacific and Australian Plates. The Pacific Plate is plunging beneath the Australian plate deep underground, at about 42 millimetres a year.
Hawke’s Bay is located right above the subduction zone which means a lot of earth movement and a lot of earthquakes. We expect earthquakes to cause the ground to shake, but the intense vibration can have other effects, especially in strong earthquakes. Crevices and cracks can open up, some areas of land will drop down or sink, while others will push upwards or tilt. The shaking will cause landslides and rockfalls sometimes blocking rivers to form dams. Liquefaction can happen where the vibration makes soil behave like liquid. Tsunami can be caused by the earthquakes or landslides and rockfalls. Learn more about these earthquake hazards at GNS Science.
Hawke's Bay sits above the subduction zone where the Pacific Plate is moving under the Australian Plate
A fault line is a fracture which the earth’s crust has moved along. The subduction interface between the Australian and Pacific Plates is the largest offshore fault in our region, and there are many other active faults onshore and offshore.
Surface faults are where a fault has started deep underground and broken through to the surface leaving visible signs, like a scar. Blind faults are buried as they slip deep underground but do not break all the way to the surface, so are harder to recognise.
See the map for generalised traces of the active surface faults in the Hawke's Bay region that have moved in the last 125,000 years. No surface traces of active faults have been mapped in the Napier and Hastings city areas because historic floods and development have covered them over. Scientists believe both cities have blind fault sources below them, including the large fault that caused the Hawke’s Bay earthquake of 1931.
Hawke’s Bay has several zones where sediment is highly susceptible to liquefaction, and where earthquakes can be large enough to cause liquefaction. There were numerous reports of liquefaction following the 1931 earthquake.
Liquefaction occurs when waterlogged sediments are vibrated by an earthquake, typically larger than magnitude 6. The soil behaves like a liquid so is no longer able to support weight and can flow down very gentle slopes. Buildings can sink, and underground pipes may rise to the surface. When the shaking stops, groundwater is squeezed out of the ground causing flooding, which can leave areas covered in mud. Low-lying areas, especially near the coast, and reclaimed land are particularly susceptible.
Liquefaction susceptibility maps for Hawke's Bay and Napier and Hastings were updated by GNS Science in 2017. Find out if liquefaction or fault lines might affect your property.
Hawke's Bay has experienced a number of significant earthquake events including the 1931 earthquake.
Hawke’s Bay has experienced many large earthquakes in the past. Most moderate to large earthquakes in Hawke's Bay have been on shallow faults close to the surface (less than 45 km deep). A few earthquakes were caused by rupture much deeper down, such as the June 1921 earthquake magnitude 7.0 located 80km deep under the Kaweka Forest.
|Date||Location||Magnitude||MM Intensity in HB|
|8 July 1843||Taihape||7.6||7-8|
|16 October 1855||Marlborough||7.5||5-6|
|23 January 1855||Wairarapa||8.2||6-8|
|23 February 1863||Waipukurau||7.5||8-9|
|9 August 1904||Cape Turnagain||7.0||6-8|
|22 November 1914||Tauranga||7.3||6-7|
|29 June 1921||Kaweka Forest||7.0||7|
|3 February 1931||North of Napier||7.8||7-9|
|13 February 1931||East of Napier||7.3||6-7|
|15 September 1932||Wairoa||6.9||7-8|
|15 March 1934||Wairoa||6.3||7|
|24 June 1942||Wairarapa||6.9||6|
|6 October 1980||Hastings||5.7||6-7|
|19 February 1990||Weber (Dannevirke)||6.1||7|
|20 December 2007||Gisborne||6.7||6-8|
|25 August 2008||Hastings||5.5||6|
|21 July 2013||Cook Strait||6.5||6|
|20 January 2014||Eketahuna||6.2||6|
|2 September 2016||East Cape||7.1||5-7|
|14 November 2016||Kaikoura||7.8||6-8|
One of the three largest historical earthquakes ever recorded in New Zealand struck Hawke's Bay at 10.47 in the morning of 3 February 1931. The magnitude MS 7.8 earthquake lasted 2 and a half minutes and was felt as far south as Timaru. It was produced by rupture on a northeast-trending buried fault, probably the Napier-Hawke Bay Fault. The initiation point (start) of the earthquake was about 20 km north east of Napier and about 30 kilometres deep. This initiation point differs from some earlier reports and improved science has changed the measurement of the earthquake too.
There was only a minor surface rupture along a 15 km stretch of the fault, but the blind fault produced an uplifted area of 1500 square kilometres with a maximum of 2.7 metres uplift. The Ahuriri Lagoon was raised 1-2 metres and partially drained, the coastline near Napier was raised and some boats moored in Napier’s harbour were left sitting on the harbour floor. However further south, part of the coast and Hastings dropped (subsided) by 1 metre. A tsunami was also experienced along parts of the Hawke Bay coast.
Some land came up and some went down in 1931. Red shows areas of uplift, while green shows areas that dropped (Map courtesy of GNS Science)
The ‘Hawke’s Bay earthquake’ was the most devastating in New Zealand history and was felt throughout New Zealand. 256 people lost their lives, either from collapsing buildings or in the devastating fires that followed the earthquake. Nearly all buildings in the central areas of Napier and Hastings were levelled as many buildings at that time were constructed of un-reinforced masonry or had poorly supported concrete facades that collapsed in the shaking. The fires that followed destroyed downtown Napier and were left to burn because the water supply in town failed. All the bridges into Napier collapsed and the main roads into Hawke’s Bay suffered severe damage.
Following the first earthquake, the region trembled with hundreds of aftershocks. Although earthquakes were difficult to measure in those days, there were appropriately 150 aftershocks in the first 12 hours, and then 525 in the 14 days after the earthquake, including a powerful Magnitude 7.3 earthquake 10 days later.
A year and a half later, there was a Magnitude 6.9 earthquake near Wairoa on 15 September 1932. It is thought this may have been instigated by the fault that ruptured in the 1931 earthquake. The shaking from this earthquake damaged buildings in Gisborne and Wairoa and caused the collapse of the Wairoa River bridge.
The 1931 earthquake not only changed our landscape – it also prompted changes in New Zealand’s approach to earthquake hazard management. New construction regulations were developed so that structures would be built to minimise damage from earthquake shaking, and were implemented by 1942. The government began to develop a system of earthquake insurance and compensation (which we know of today as the Earthquake Commission (EQC)). Civil defence strategies were put into action to ensure that public safety and relief would be taken care of in future earthquakes.
All the cities and towns of Hawke’s Bay were devastated by New Zealand's deadliest earthquake. There were 256 people who died - 161 in Napier, 93 in Hastings and 2 in Wairoa. Many thousands required medical treatment.
Here’s a breakdown of some of the key facts about this earthquake. And one fiction! - people often describe a hot, sultry day as being ‘earthquake weather’, possibly because 3 Feb 1931 was a hot summer day, but earthquakes happen in all sorts of weather.
The Hawke's Bay earthquake was the worst natural disaster ever recorded in New Zealand. People who lived through the earthquake had some dramatic stories to tell and some are told below.
The following quotes are from 'The Shock of '31' By Geoff Conly.
Mr P.W Barlow, chief surveyor with the Napier branch of the Lands and Survey Department, had just completed drafts of letters to be typed when the room began to shake. He pushed his large swivel chair out from his desk, lay on the floor, put his legs under the desk and his head under the chair. He felt the culmination of the earthquake as a violent shake, 'similar to the shaking a fox terrier given when killing a rat' he said. Then came the big crash. Bricks were raining into the room and the dust was so thick he could not see his hand 25 centimetres away from his face.
Wilson Wright was 5 years old and never thought the sound of school bells would be replaced by the sound of an earthquake. At home, music from a gramophone echoed through his parents' house - his mother was busy with the household chores. 'The room shook, the chimney fell, and she ran outside as the second shock came,' said Mr Wright. His father, manager of the freezing works at Pakipaki, escaped injury but found himself in an unlucky position when the quake struck. 'He stepped out on to the veranda roof over the railway siding, just as it collapsed. He described it was like coming down in a lift, except he was chased by falling bricks. Afterwards he had the grim task of organising search parties to collect the dead bodies.'
Mavis Rowe was 16 when the earthquake struck and she was working at a Shamrock Street home. 'It was a hazy, muggy sort of day. Two of us must have been up the front of the house … and there was just this awful noise. For a minute you'd think a truck had run into the house,' she said. 'It was so noisy with the house creaking and groaning and the chimneys coming down. You couldn't in your wildest dream imagine what those quakes were like. There was stuff falling all the time. I grabbed Auntie'. They found they couldn't get out of the back of the house, so they hurried back down the long hall toward the front door. But the quake had jammed the door shut. 'I was all prepared to get a shoe and break a window in the bedroom and push Auntie out. But another big jolt started and the door flew open. I pushed her down the hall and she never flew down those steps so fast in all her life!' Outside, a wooden fence was swaying down and touching a lemon tree before swaying back up again. 'I thought, the ground will open up and swallow us, but there's nothing we can do about it' she says. Across the road, a woman was calling 'my crystal, all my crystal'. Mavis said 'I thought: what does she want crystal for? It's the end of the world, she won't need that'.
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