“A logarithmic scale used to rate the strength or total energy of earthquakes. The scale has no upper limit but usually ranges from 1 to 9. Because it is logarithmic, an earthquake rated as 5 is ten times as powerful as one rated as 4. An earthquake with a magnitude of 1 is detectable only by seismographs; one with a magnitude of 7 is a major earthquake. The Richter scale is named after the American seismologist Charles Francis Richter (1900-1985).”
The American Heritage® Science Dictionary Copyright © 2005 by Houghton Mifflin Company.
And if there is an earthquake, that means that something is happening underground. For a Powers of 10 project, make a map of the location of the earthquake and then draw in where the shifting of tectonic plates is happening underground in one color. And then draw concentric circles showing how far away the earthquake was felt in another color.