GeoNet and Earthquakes
GeoNet uses automatic locations so we can locate and display every earthquake as soon as we receive enough data. Displaying 20,000 earthquakes a year on the website is a challenge to the layout of the website content! We do two things - firstly, we split recent earthquakes into two streams; All and Felt. As you may guess All is everything that has been located. Felt is earthquakes that might have been felt. Currently we use an algorithm (a set of calculation rules) to determine if an earthquake might have been felt. Secondly, we present earthquakes grouped in the major regions around New Zealand. Each region has an All and Felt list of earthquakes. It's useful to remember that a large earthquake in Wellington could appear in the Felt list for Christchurch even though it's outside the Christchurch region. That's why there are two intensity labels: one for the maximum intensity that could be expected, and one for the maximum intensity expected in that particular region.
Other significant events within the greater south-west Pacific region may be detected by our equipment, but we do not routinely locate these as the geometry of our recording network does not allow accurate epicentres and magnitudes to be determined. Details about these earthquakes are available from the United States Geological Survey.
If you have felt an earthquake recently, we would like to know where you were and what happened to you. This information will help us understand how your area might respond in future earthquakes. Your input will be used to make maps of how the intensity of shaking was distributed over the area which felt the earthquake. The questionnaire should only take a few minutes to complete.
Computers do the ceaseless job of monitoring seismic data looking for possible earthquakes. Once one has been initially detected, the location and magnitude become refined over a number of minutes as more data from further stations arrives. For the bigger quakes, we get a Duty Officer to confirm the final details.
Find out about some of New Zealand's largest historical earthquakes.
The size of an earthquake is often described using magnitude, which is the amount of energy released during an earthquake. However, not all of the energy released in an earthquake will necessarily be felt at the surface, depending on the earthquake's depth. In New Zealand, where earthquakes occur from near the surface right down to a depth of over 600 km, the Modified Mercalli intensity scale is a better indicator of an earthquake's effects on people and their environment.
The GeoNet project locates between 50 and 80 earthquakes each day, or about 20,000 a year. How do the numbers break down by year and size?
Frequently asked questions about earthquakes.
A glossary of earthquake-related terms.
A list of links to other websites with further earthquake-related information.