How do we know about Earth movements?
Aotearoa New Zealand experiences a lot of geological activity – the land is right at the junction of the Australian and Pacific tectonic plates – making it a shaky place to live! The Pacific plate is being forced down (subducted) under the Australian plate.
GNS Science reports the country receives over 15,000 earthquakes each year but only 100–150 of the quakes are large enough to be felt. We know about the smaller movements because they are recorded by seismographs. These machines are very sensitive to earth movements, but some movements are so small and occur over time that they don’t register. These movements are called slow slip events.
Tectonic plates, volcanoes and earthquakes
Far underneath the ground we walk on, the Earth is covered with tectonic plates. You can think of tectonic plates as puzzle pieces. Earthquakes and volcanoes often happen where the pieces meet.
Point of interest
Can you see the Southern Alps on the map? What is happening to make them a little taller every year?
Scientists were surprised to discover that large areas of land in Te Ika-a-Māui North Island are silently and slowly moving towards the east. The movement is very, very slow. In human terms, imagine standing at one spot and taking more than 2 weeks to move a couple of millimetres. Now you can see why slow slips weren’t even noticed in Aotearoa until 2002.
Exploring the slow slip mystery
Slow slips were first observed in Japan and Canada. Scientists in Aotearoa began their own observations by setting up networks of continuously recording global positioning system (CGPS) stations. There are over 50 monitoring sites across the North, South and Chatham Islands. Satellites send signals to the receivers at these sites, enabling the stations to record very precise positions on the Earth’s surface. This continuous sending and receiving allows scientists to measure even the smallest of movements – and the bigger ones too.
GNS Science reported more than a dozen slow slip events in the first 10 years of monitoring. They have occurred in Gisborne, Hastings, Wanganui, Ashhurst, Dannevirke and Paekākāriki, and offshore in the Gisborne and Hawke’s Bay regions.
GPS station
Tiny ground movements can be detected by using a network of continuously recording global positioning system (GPS) stations.
A GPS station is also known as a GPS receiver.
Why we need to monitor slow slips
If the ground is moving so slowly, why go to the time and effort to track movements of just a few millimetres? It’s because scientists want to know if there is a relationship between slow slips and earthquakes. Sometimes it appears that slow slips can relieve the stres s that builds up in fault lines. Other times it appears that slow slips increase the stress in surrounding areas and push the fault closer to rupture (breaking). Collecting data about slow slips provides a better understanding of this relationship. It might also help to inform models that warn us about earthquakes.
Earth movements satellite mission
Using satellite and GPS technology, scientists can gather real-time data about the movement of the Earth’s crust. Some of this movement is so small it is not felt on the land, but it provides important data for understanding the processes and predictions of earthquakes and other hazards.
This animated video is part of the Build a satellite interactive. To find out more about using satellites to track Earth movements, see the article How do we know about Earth movements? then follow up with the activity Analysing satellite data to track Earth movements.
Build a satellite to track Earth movements
Have a go at building a fit-for-purpose satellite to monitor slow slips! Choose the ‘Monitor Earth movements’ scenario. Once you’ve received the GNSS data, use this activity to analyse the slow slip movements around Māhia Peninsula .
Build a satellite
This interactive simulation is designed to develop students’ understanding of satellites and their usefulness with real-life research in Aotearoa New Zealand. The simulation requires users to build their knowledge and understanding about the requirements of each mission along with the satellite components needed to successfully launch a satellite that is fit for the mission’s purpose.
The simulation has three missions:
Find dark vessels fishing illegally
Track an albatross population
Monitor Earth movements
At each stage, there is access to a help button and links to additional resources that will support student learning in order to make accurate decisions throughout the satellite build and launch.
Simulation instructions
Click and drag components onto the satellite outline. Components can be added and removed. You will need to select all of the essential components as well as choose the correct payload component for your mission. Choosing the wrong payload means your satellite will not be able to collect data. Hover your mouse or finger over and select the three dots on each component to find out more information about its purpose.
Select a suitable orbit for your satellite’s mission. Choosing the wrong orbit means your satellite won’t be able to collect data.
For optimal viewing, use landscape orientation when using a tablet or iPad.
This is a simulation, so please note there may be small inaccuracies and satellite components and orbits are not to scale.
See the activity Build a satellite for a mission for a mission for additional support in using this interactive simulation.
Related content
These resources provide helpful background information.
Read more about building satellites.
Discover more about using satellites to track:
Activity ideas
Use the data the satellites collect during the simulation to analyse:
albatross nesting sites on a Chatham Islands sea stack
slow slip Earth movements near the East Coast’s Māhia Peninsula.
Consider doing the activity Interpreting observations from satellite images prior to these activities. It introduces strategies that are useful when interpreting satellite images.
Acknowledgement
This resource has been produced with funding from the Ministry of Business, Innovation and Employment and the support of the New Zealand Space Agency.
Rights: Crown copyright
Ministry of Business, Innovation and Employment and the New Zealand Space Agency
The New Zealand Space Agency, part of the Ministry of Business, Innovation and Employment, is the lead government agency for space policy, regulation and sector development.
Related content
Earthquake resources – planning pathways provides pedagogical insights and curates Hub resources into key science and technology concepts.
The JOIDES Resolution research ship used expedition #375 to explore slow slips.
Related activities
Explore tectonic plate concepts by making tectonic sandwiches and tectonic jigsaw puzzles.
Useful links
The Kaikōura earthquake in November 2016 caused a slow slip 250–600 km away from the New Zealand Aotearoa coastline on the shallow part of the Hikurangi subduction zone. Read this media article with Dr Laura Wallace to learn about how this earthquake has advanced scientific knowledge of slow slip events.
Acknowledgement
This resource has been produced with funding from the Ministry of Business, n and Employment and the support of the New Zealand Space Agency.
Ministry of Business, Innovation and Employment and the New Zealand Space Agency
The New Zealand Space Agency, part of the Ministry of Business, Innovation and Employment, is the lead government agency for space policy, regulation and sector development.
