Foundation, Concrete and Earthquake Engineering

Difference Between Magnitude and Intensity of Earthquakes

The stain energy released during an earthquake travels as seismic waves in all directions through the earth's layer, reflecting and refracting at each interface. These vibrations are more intense nearer the center of disturbance and these become feeble and ultimately die out, as the distance increased. Generally a common problem occur merging magnitude with intensity.


Magnitude is a quantitative measure of the actual size of the earthquake. Based on maximum displacement, magnitude is determined and through magnitude energy released can be computed.

Intensity :

Intensity is a qualitative measure of the actual shaking at a location during an earthquake. Intensity is determined from three features of shaking -

1) perception by people and animal

2) performance of building

3) changes to natural surrounding.

Basic Difference

Magnitude defines size of a earthquake. As example, the size of an earthquake can be measured by the amount of strain energy released by the fault rupture. On the other hand, intensity is an indicator of the severity of shaking generated at given location. There is no doubt that the severity of shaking is much higher near epicenter than farther away.

This means that the magnitude of the earthquake is a single value for a given earthquake but different locations experience different degree of intensity for same quake.

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