Learn about Earthquakes

This image represents one day’s recording of the seismometer located at Nelson, New Zealand.

The time shown at the top right is the time when this image was last refreshed. Each horizontal line represents 30 minutes, each vertical line is spaced 1 minute apart; 24 hours of recording are displayed in total. The most recent signal is drawn at the bottom right hand corner of the drum. So read the traces from right to left, bottom to top, to get from the most recent to the oldest signals. The trace will appear red if the signals are very large; this means they have been clipped to stop them overwriting too much of the surrounding image.

Source: Courtesy of NZ GeoNet

What to do when there’s an Earthquake?

4.5, 5.6, 6.7 – what do those magnitude numbers really mean?

The Richter Scale is an attempt to describe the size of an earthquake. It measures the ground movement at the source of the earthquake. It’s important to know that the scale is logarithmic – that means a magnitude 7 earthquake produces vibrations ten times greater than those of a magnitude 6 shake, and a hundred times greater than those of a magnitude 5 shake.

But a magnitude 7 earthquake releases about 30 times more energy than a magnitude 6 shake, and about a thousand times more than a magnitude 5!

And all that energy has to go somewhere.

Magnitude	Effects	World-wide every year
2.5 – 5.4	Often felt; minor damage	30,000
5.5 – 6.0	Slight damage to buildings & structures	500
6.1 – 6.9	May cause much damage in populated areas	100
7.0 – 7.9	Major damage	20
8.0 +	Great damage; may totally destroy communities	1 every 5 – 10 years