New Zealand experiences thousands of earthquakes every year. Most are either very deep or centred well offshore, and cause little damage or injury. But a large earthquake could happen any time and can be followed by aftershocks that continue for a long time.
New Zealand lies on the boundary of the Pacific and Australian tectonic plates.
Tectonic plates are always on the move. Tension builds up as they scrape over, under or past each other. In some places, movement between the plates is happening all the time, and this causes frequent small or moderate earthquakes. Other areas, where the movement is not constant, are likely to get stronger quakes separated by longer periods of time because the tension builds up and then is released in a bigger movement.
Most (though not all) earthquakes occur at faults, which are breaks that go deep within the Earth, caused by the movement of these plates. The point under the ground where the earthquake actually begins is called the hypocentre or focus. The place directly above it on the surface is called the epicentre.
Earthquakes cause vibration waves to travel through the ground. The first sign of a quake is often the rumbling sound caused by the ‘P’ (primary or push) waves travelling at about 20,000 kilometres an hour. That is twenty times faster than a jet aircraft. The ‘S’ (secondary or shear) waves follow along at about 10,000 kilometres an hour. They cause the main rolling and shaking effects of an earthquake.
Strong earthquakes change the land, lifting it up or dropping it down. They cause landslides and rockfalls on hills and sometimes make solid land behave like a wobbling liquid (liquefaction). All of these effects can damage buildings, roads, pipes in the ground, electricity and telephone networks. Earthquakes create very strong shaking, which can damage and sometimes collapse buildings. Very big earthquakes in the sea floor sometimes create tsunami waves.
There are two ways of measuring earthquakes.
The Richter scale measures the energy released by an earthquake, which is called the earthquake's magnitude. The Magnitude (M) scale ranges from one to ten (the largest so far was the 9.5 Chilean earthquake in 1960). It is a logarithmic scale, which means that a magnitude seven earthquake is 32 times as powerful as a magnitude six quake. The 1855 Wellington earthquake had an estimated magnitude of 8.2. Napier was struck by an M 7.8 quake in 1931 and Kaikoura by an M 7.8 quake in 2016.
The Modified Mercalli (MM) scale is a measure of intensity based on the effects of the earthquake on people and buildings. This scale ranges from MM1 (smallest) to MM12 (largest). The 1855 Wellington and 1931 Napier earthquakes were both MM10 at their epicentres. The shaking intensity lessens as you get further away from the epicentre. An earthquake can only have one Magnitude value (how much energy), but it can have a range of intensities from very strong shaking if you are close, to very mild shaking if you are further away.
Practise your earthquake drill: Drop, Cover and Hold.
Talk with your family and prepare an emergency plan.
Identify safe places close to you at home or school.
Visit the Earthquake Commission's website for more information on making your home safer.
Drop, Cover and Hold.
Stay where you are until the
If inside, stay inside; if outside
Do not attempt to run outside.
DROP down on your hands and knees. This protects you from falling but lets you move if you need to.
COVER your head and neck (or your entire body if possible) under a sturdy table or desk (if it is within a few steps of you). If there is no shelter nearby, cover your head and neck with your arms and hands.
HOLD on to your shelter (or your position to protect your head and neck) until the shaking stops. If the shaking shifts your shelter around, move with it.
Listen to and follow all instructions from adults or the radio.
Stay Calm. If you can, help others who may need it.
Watch out for possible hazards.
Remember there may be some aftershocks.
Remember your emergency plan and follow it if it is safe to do so.
Find out more about what to do before, during and after an earthquake.
Draw a plan of your house showing places to shelter in an earthquake. Show where to turn off water, electricity and gas. Share your plan with a friend and ask if they have thought of doing their own.
Make a plan with your family to get through an emergency. Think about the things you need every day and work out what you would do if you didn't have them. Fill in this online form then print it out, stick it on the fridge and make sure everyone knows the plan.
Find out about past earthquakes that have happened in your region.
Learnz provides virtual field trips. In this field trip, experts will take you to remote locations to help you better understand what causes natural disasters such as tsunami, earthquakes and landslides, and how you can manage the risk of these events.
Earthquakes 101 is part of a series of natural disaster videos produced by National Geographic.
On QuakeStories, survivors of the Christchurch earthquakes tell their stories.
Learnz provides virtual field trips. In this field trip you will learn from experts what caused the Canterbury Earthquakes.
A resource designed to help students develop an understanding about earthquakes in New Zealand, including why we get them and how we measure them.
Earthquake-related articles, activities, events and cool jobs from STEM-Works.
In this activity, students use data on historical earthquakes to identify when and where they occurred and make predictions about future earthquakes.
During the 2020 COVID-19 lockdown, GeoNet asked the public for questions they have always wanted to know the answers to on earthquakes, volcanoes, landslides and tsunami. This YouTube playlist is a series of short videos answering these questions.
Earthquakes, floods, landslides, storms, tsunami and volcanic activity can be frightening because they can strike at any time and often without warning. Explore the types of emergencies below and learn better ways to prepare.