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ARCHIVED - How do we measure earthquakes?

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Earthquake strength is measured in two ways: magnitude and intensity.Earthquake strength is measured in two ways: magnitude and intensity.

Magnitude is a measure of the energy released at the earthquake source.Magnitude is a measure of the energy released at the earthquake source. But how do scientists measure this?

A network of sensors, called seismometers, is used to record earthquakes.A network of sensors, called seismometers, is used to record earthquakes.

An earthquake’s magnitude is calculated based on the ground motion recorded by each seismometer and the distance of that seismometer from the earthquake.An earthquake’s magnitude is calculated based on the ground motion recorded by each seismometer and the distance of that seismometer from the earthquake.

For each unit of increase in magnitude, the amount of ground motion increases by a factor of 10.For each unit of increase in magnitude, the amount of ground motion increases by a factor of 10.

This means that the amount of ground motion for a magnitude 6 earthquake is 10 times greater than for a magnitude 5…This means that the amount of ground motion for a magnitude 6 earthquake is 10 times greater than for a magnitude 5…

…and 100 times greater than for a magnitude 4.…and 100 times greater than for a magnitude 4.

Intensity represents the strength of shaking we feel. It depends not only on the magnitude of the earthquake but also our distance from the epicentre... Intensity represents the strength of shaking we feel. It depends not only on the magnitude of the earthquake but also our distance from the epicentre...

…and whether we are in a building……and whether we are in a building

  …or outside.…or outside.

The underlying geology also affects intensity. People on soft soils usually experience longer and greater shaking than those on bedrock or stiff soils.The underlying geology also affects intensity. People on soft soils usually experience longer and greater shaking than those on bedrock or stiff soils.

Remember:  Magnitude = energy released at the source. Intensity = strength of shaking that we feel.Remember:  Magnitude = energy released at the source. Intensity = strength of shaking that we feel.
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ISSN 1927-0275 = Dimensions (Ottawa. Online)