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Gallery 3

# Momentous Magnitudes

The Moment Magnitude scale is used to measure the strength of earthquakes, increases by a factor of 10.

## How it works

Select an earthquake magnitude on the scale by turning the dial. Press the 'start' button and place your hands on the 'Table'. Feel the earthquake!

## Things to try or ask around the exhibit

• At what point on the scale can you start to feel vibrations?
• How much stronger is each point on the scale compared to the last point?

## Background

Scientists have used several methods to measure earthquakes, although some like the Richter scale aren’t used much anymore. Modern measurements use the moment magnitude, which compares the rock’s rigidity to the amount of rock movement and the distance moved.
How an earthquake feels depends on its magnitude and your distance from the epicentre. You can generally only feel earthquakes with a magnitude of 3 or more whilst magnitude 6 or more can cause considerable damage.

Every time the magnitude goes up by 1 ground movement increases ten times, so magnitude 5 moves the ground ten times more than magnitude 4. This uses thirty two times more energy.

## Finding the science in your world

Another measure often used to compare earthquakes is an intensity scale called the Modified Mercalli Scale. This relies on what people actually see happening and their distance away from the epicentre of an earthquake. So a large city and a deserted area may both experience an earthquake of similar magnitude on the Richter scale, but the city will rate the earthquake higher on the Mercalli scale because there is more damage to buildings and services.