Rū whenua Earthquakes

An earthquake is the fracturing of rock and release of energy beneath the Earth’s surface.

Earthquakes can result in ground shaking, surface fault rupture, liquefaction, and ground deformation. Earthquakes can also trigger other hazards such as landslides, tsunami, floods, fires and gas leaks.

Earthquakes cause physical damage to people, the environment, buildings and infrastructure (including transportation, water, electricity and telecommunication networks). Recent events have also shown us what a profound psychological and emotional impact they can have on our family life and communities.

Earthquakes are described by their magnitude and their intensity. Magnitude measures the energy released during an earthquake, while intensity describes the severity of shaking experienced on the ground surface.

New Zealand lies on the boundary of the Pacific and Australian tectonic plates, therefore earthquakes happen here every day. Most are too small, too deep, or too far offshore to be noticed. However, a strong, damaging earthquake can happen at any time.

Every year, GeoNet locates over 15,000 earthquakes in New Zealand. About 100 to 150 earthquakes per year are large enough to be felt. Earthquakes tend to happen in clusters or "swarms" that may last for some weeks or months in a particular area.

From historic trends and records dating from the 1840s, we know that New Zealand can expect one magnitude 6 earthquake every year on average, and one magnitude 7 every ten years on average. Since 1840, we have experienced one earthquake larger than magnitude 8, the M8.2 1855 Wairarapa earthquake, which caused the surface of the Earth to be offset by up to 18 metres.

Since 2000, New Zealand’s largest earthquake was the M7.8 Kaikōura earthquake in November 2016, but the most damaging was the M6.2 Christchurch earthquake in February 2011, which resulted in 185 deaths.

Ground shaking is the movement of the earth’s surface, produced by energy waves travelling through the earth and along its surface. It is one of the main causes of earthquake damage to buildings and infrastructure.

Surface fault rupture is the ripping or warping of the ground surface as the ground on one side of a fault moves relative to the other. This mostly happens in moderate to large earthquakes (M6.5 and above).

Liquefaction occurs when partially saturated soils are disturbed by intense shaking and lose their strength and stiffness. This often results in unpredictable settlement of the ground and the ejection of a slurry like mixture of soil and water.

Ground deformation is a change to the land surface, such as lowering or collapse (subsidence) or raising or swelling (uplift).

Land deformation can directly damage buildings and infrastructure, cause landslides, and change the risk of flooding.

Buildings, like your home, are designed to resist earthquake shaking. They do this by combining strength and stiffness of the building structure. Some shaking and movement are okay, but moderate to large earthquakes can result in more damage. The most common parts of your home that can be damaged in an earthquake include:

• chimneys
• foundations
• slopes and retaining walls
• wall and roof linings
• large or heavy furniture and appliances

• Learn how to make your home saferopen_in_new
• Search your address in the Natural Hazards Portal to find out which hazards may affect your property.
• Read more about earthquakesopen_in_new and how they can affect people and places.
• Check that you have the right insurance in placeopen_in_new, including home insurance that may qualify you for natural hazards cover.
• Check your local council website for information about local hazards and emergency planning in your area.