Earthquake Intensity—Introduction to 4 Modules

3min 10s Novice

Seismic intensity is the shaking you experience during an earthquake. Unlike an earthquake's magnitude, which is a measure of the energy released and is the same for all locations, the intensity of shaking you feel depends on your location.

Seismic intensity is controlled by four main factors:

    • Magnitude
    • Distance from the epicenter
    • Depth to the hypocenter
    • Local rock and soil conditions

Module 1—Effect of magnitude on intensity of ground shaking
The magnitude, or size, of an earthquake is related to the total amount of energy released by the earthquake source. So a given earthquake has only one magnitude, but will produce different intensities of ground shaking at different locations. In this animation we use a light bulb to describe the difference between magnitude and intensity.
Animation Novice
Module 2—Distance from epicenter; effect on ground shaking
Intensity varies depending how far you are from the epicenter. The light from a lamp is less bright the farther away we are from the lamp. By analogy, we expect shaking to decrease with distance away from the earthquake.
Animation Novice
Module 3—Effect of depth on intensity of ground shaking
Earthquakes occur in the Earth, not on Earth’s surface. That means, if the earthquake is shallow, the shaking will be intense. If the earthquake is deep, the seismic waves attenuate, or grow weaker on their way to the surface.
Animation Novice
Module 4—Effect of rock and soil on shaking
Local rock and soil conditions influence ground shaking intensity and the resulting damage. Seismic waves will amplify when entering softer soils compared to hard bedrock.
Animation Novice

Related Animations

Earthquake Intensity

Earthquake intensity (what is felt during an earthquake at any given location) is often mistaken for earthquake magnitude (the instrumentally measured size of that earthquake). This animation describes the main factors that contribute to differing intensities using examples of earthquakes. Produced in collaboration with the U.S. Geological Survey.

Animation Novice
Magnitude Explained: Moment Magnitude vs. Richter Scale

The "moment magnitude" scale has replaced the Richter scale for large earthquakes. Scientists have developed far-more sensitive seismometers that, with faster computers, have enabled them to record & interpret a broader spectrum of seismic signals than was possible in the 1930's, when the Richter magnitude was developed. Find out what scientists learn from seismograms.

Animation Novice