Investigating earthquakes – introduction
Shaky New Zealand
About 14,000 earthquakes are recorded in and around New Zealand every year. Fortunately, most of them are too small for us to feel at the surface. However, many of us have felt the shake of an earthquake, and there are some big ones that have become part of New Zealand history. The earthquakes in and around Christchurch in February 2011 and Kaikōura in 2016 were devastating, and reminded people around the country that they too must be prepared for ‘the big one’.
Earthquake damage, Christchurch, September 2010
The Darfield earthquake of September 2010 caused much damage in Christchurch, 40 km away. Vertical movement pushed this storm drain up through the road in the suburb of Brooklands.
(Earthquakes are measured on the Richter scale.)
When?
Where?
How big?
What happened?
23 January 1855
Wairarapa
8.2
Land raised in Wellington region
17 June 1929
Buller, South Island
7.8
Much destruction in Murchison area
3 February 1931
Hawkes Bay
7.8
Napier and Hastings badly damaged, land uplifted, 256 people killed
24 May 1968
Īnangahua Junction
7.1
This shallow earthquake killed 3 people and caused many slips and damaged roads and bridges
2 March 1987
Edgecumbe
6.6
Much faulting and land sinking
4 September 2010
Christchurch and surrounds
7.1
Many buildings damaged, land shifted, but few people injured
22 February 2011
Christchurch and surrounds
6.3
Widespread destruction of buildings and services, hundreds of people injured and 185 killed
14 November 2016Kaikoura and further7.8Extensive destruction of buildings and services, land uplifted, widly felt, 2 deaths
The occurrence of destructive earthquakes is unpredictable, but communities and rescue organisations prepare as much as they can. Research is going on to try and understand the geological activity under New Zealand and also to devise ways of making buildings safer with seismic engineering. Learn about seismic engineering at Canterbury University and find out how experts like Dr Bill Robinson use base isolators to protect important buildings such as Parliament House and the Museum of New Zealand Te Papa Tongarewa.
Alpine Fault trace
The Alpine Fault trace can be seen near the Jerry and Pyke Rivers in the South Island.
Why does New Zealand get earthquakes?
Earthquakes and volcanoes are common around the world where one tectonic plate is sinking under another at a subduction zone. Look for New Zealand on a world map of tectonic plates. It is right at the junction of the Australian and Pacific plates – a shaky place! There is a lot of geological activity here, including earthquakes, volcanoes, mountain building, faulting and erosion. Find out more in the article Plate tectonics.
Discover the two violent tectonic events that shaped the continent Zealandia and what makes this submerged continent so different to others.
What causes earthquakes?
At a subduction zone, two tectonic plates try to pass each other. Along faults, rocks grind past each other, some more easily than others. Instead of sliding, some rocks lock together – but they are still being pushed, so they bend and distort, and stresses build up. Eventually, the pressure becomes too much, and the two sides of a fault jerk past each other. This releases stored energy as shock waves (called seismic waves) that travel out from the focus through the surrounding rock, sometimes to the other side of the world. The articles Moulding the Earth and Liquefaction disucss what happens as a result of these stresses and pressures.
Glenroy River fault trace
The Glenroy River in the Tasman Region of the South Island follows part of the Alpine Fault.
The seismic waves travel at different speeds. The faster P-waves reach the surface first, followed by the slower S-waves, which can cause the ground to shudder backwards and forwards. Both types of waves set off new waves at the surface, around the epicentre, which cause most of any damage.
Scientists use seismographs to measure when the seismic waves reach three different points, and they can work out where the focus and epicenter are. They also use the waves to work out the magnitude of the earthquake, normally measured on the Richter scale.
Earthquake research
Earthquakes are important in the geology of New Zealand, and they have the potential to cause damage and affect people’s lives. Because of this, there is a lot of research going on to try and understand them more. Some of the research focuses on the Alpine Fault – and the squishy zone below it. Scientists from other countries come to New Zealand to help build up a world picture of tectonic activity. Find out how teaching fellow Keith Machin lent them a hand.
Research includes trying to:
understand what happens inside the Earth
understand the details of how earthquakes are caused
increase the accuracy of measurements and forecasting
monitor earthquake activity to help emergency and long-term planning
understand seismic waves and surface effects so that buildings can be made safer
find out more about the forces shaping New Zealand
explain newly recorded events, such as slow slips, about which Dr Laura Wallace is an expert.
Slow slip event – an animation
Slow slips are silent earthquakes that occur below the Earth’s surface over a large area, unlike traditional earthquakes we feel that occur in a relatively small region.
Before discovering slow slip events, earthquakes were thought to be the only way the Earth’s crust could relieve the pent-up stresses caused by the moving tectonic plates.
Scientists are now actively working to understand the relationship between slow slips and earthquakes. There is evidence of earthquake swarms accompanying some slow slip events, suggesting a slow slip may increase stress in surrounding areas and could push an already stressed fault closer to rupture. However, in other cases, slow slip events can relieve stress on a fault, and this might postpone an earthquake.
Understanding the relationship between slow slip events and earthquakes and the collation of slow slip data will enable better earthquake forecast modelling.
This animation is a visualisation of a slow slip event.
Take up the challenge
Use the teaching resource Earthquakes New Zealand to learn about seven activities designed to help students develop an understanding about earthquakes in New Zealand, including why we get them and how we measure them. Something creepy is happening explores tectonic movements called slow slips. The Best base isolator uses a physical model to investigate the effectiveness of different properties for base isolators. There is even a unit plan to help middle and upper primary classrooms get started.
Explore this resource for teachers from Te Papa and EQC Building an earthquake-ready future. It is aimed at curriculum levels 2–5 covering science, social studies and literacy.
Question bank
The Investigating earthquakes – question bank provides a list of questions about earthquakes and places where their answers can be found. The questions support an inquiry approach.
Key terms
For explanations of key concepts, see Investigating earthquakes – key terms.
Timeline
Explore the timeline to look at some of the historical aspects of earthquakes. Find out how our understanding of what causes earthquakes has changed.
Planning pathways
Realistic contexts connect students to authentic scientific processes and purposes. It’s all explained in Earthquakes resources – planning pathways.
Related content
In 2018, scientists spent two months aboard the JOIDES Resolution research ship exploring the Hikurangi subduction margin. Information about their work, and other resources, are curated in this article.
For younger students, see the resources mentioned in the On shaky ground article.
Explore the range of resources we have on volcanoes.
Earthquakes is a collection supports the House of Science Earthquakes resource kit – but it is also useful for anyone exploring Rūaumoko, what's inside the Earth, plate tectonics, seismic waves and engineering designed to keep us safe.
Useful links
Check out our Earthquakes Pinterest board, it's full of ideas for additional resources.
Information from Te Ara on the focus and epicentre of an earthquake.
