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What is the difference between intensity scales and magnitude scales?

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Welcome to CoreFacts, where we're always short on time and big on science. I'm Brian Campbell. Today's question is ...

What is the difference between intensity scales and magnitude scales?

Intensity scales, like the Modified Mercalli Scale and the Rossi-Forel scale, measure the amount of shaking at a particular location. So the intensity of an earthquake will vary depending on where you are. Sometimes earthquakes are referred to by the maximum intensity they produce.

Magnitude scales, like the Richter magnitude and moment magnitude, measure the size of the earthquake at its source. So they do not depend on where the measurement is made. Often, several slightly different magnitudes are reported for an earthquake. This happens because the relation between the seismic measurements and the magnitude is complex and different procedures will often give slightly different magnitudes for the same earthquake.

And now you know.  Join us again every week for a new CoreFact.  For other CoreFacts, or for CoreCast, our in-depth science podcast, go to  If you'd like to have a question featured on our show, give us an e-mail at or a phone call at 703-648-5600.  Remember, long distance fees do apply.  CoreFacts is a product of the U.S. Geological Survey, Department of the Interior.

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Title: What is the difference between intensity scales and magnitude scales?


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Date Recorded: 4/15/2009

Usage: This audio file is public domain/of free use unless otherwise stated. Please refer to the USGS Copyright section for how to credit this audio.

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