Four major fault lines are within the Wellington region, making the Hutt Valley vulnerable to earthquakes. A major earthquake, dependent on size and location, could affect the Hutt Valley quite badly, damaging properties and disrupting essential services.
There are no warning systems able to alert the community of an earthquake. The best defence is a prepared, resilient, community able to respond and recover efficiently with its resources.
The Hutt Valley Emergency Management Office (HVEMO) has plans in place to respond effectively, enabling prompt recovery of essential community services, and facilitate the return of the community to its normal living standards.
Earthquake Information
Earth's Plates
NZ lies over two large sections of the earth's crust known as plates - the Australian and the Pacific plates. Movement between these plates causes the earthquake activity in our country. 20 - 30 km under the ground the Pacific Plate is being forced under the Australian Plate.
Fault Lines
The Hutt Valley is vulnerable to earthquake. There are four major faultlines within the Wellington region, and activity on any of these faults is likely, however New Zealand has other faultlines and amplified ground shaking from a radius of about 200 km can affect the Hutt Valley.
Biggest hazard
The biggest hazard is a major earthquake on the Wellington fault which runs from Cook Strait, through the Karori Reservoir, Thorndon, along the northwest side of the harbour and the west side of the Hutt Valley. This hazard is greatest because of the population centres, and moves more frequently than any other faults in the region.
Earthquake effects
This depends on the size, location and on the type of soil in each locality. Parts of the Hutt Valley are made up of flexible soil, which means the effects of the shaking could be amplified up to 10 - 15 times from a remote event.
After Shocks
Aftershocks may occur after the main quake. They can be enough to further damage already dangerous structures, and can occur frequently over the following few weeks.
Damage to community
Dependent on size and location of the earthquake pockets of the Hutt Valley could experience major damage, while other areas may have only minor disruption.
Major Disruptions to Utilities
A major earthquake in the Wellington Region would cause disruptions to utilities including, communications, power, gas, roads, water services, and sewerage systems. It would take at least three days for some of these utilities to be partially restored.
Other consequences of earthquake
Tsunami, landslides, ground rupture and liquefaction are hazards that could occur as a result of earthquakes. Fires and damaged building, roads and bridges are secondary problems.
Warnings
There are no warning systems in place for earthquake. Research continues in this field.
Community Education
Seminars, publications and brochures, annual campaigns, talks to community groups and businesses, planning with education facilities and other at-risk organisations are part of the actions undertaken by the HVEMO in preparing the community for a disaster.
Community Preparedness
Take action in your home to reduce the risk, including: check chimney is secure, secure water cylinder and header tank, fix bookshelves and heavy furniture to walls, place heavier items closer to the floor.
Take out earthquake insurance and keep it up to date. Organise a survival kit. Refer to preparedness information.
Initial response
Initial response to a major earthquake would be to declare a state of Civil Defence Emergency.
Headquarters Activation
Civil Defence headquarters would be activated. Civil Defence staff, emergency services and liaison organisations would report to headquarters. Contact established and maintained with regional Civil Defence.
CD Centres
Civil Defence Centres would be activated. Headquarters would contact the centres by radio to ensure they are operational. People requiring assistance should go to their nearest CD centre.
Public Information
Civil Defence would provide information and advice to the public through broadcasts on radio stations. The situation with the power will determine how quickly broadcasting could commence.
Priorities
Safety of the community is the first priority, isolating any hazards, rescue and medical assistance, assembling information, location assessment, community welfare, essential services restoration are some of the priorities that would be considered.
Worst known earthquakes
In 1848 a series of earthquakes occurred over several days, the strongest had a Richter scale magnitude of 7.1. In 1855 an earthquake of Richter scale magnitude 8.1 was felt in the Wellington and Wairarapa region - buildings were damaged and the shoreline rose 6 metres.
Probability
There is a 55 - 99% chance of one of the fault lines rupturing in the next 100 years.