What is the Richter scale?
The Richter scale is a method for measuring the size of earthquakes, created by Charles Richter in 1935. Each whole number represents about 10 times more ground shaking and about 32 times more energy.
Charles Richter, a seismologist in California, developed the scale with Beno Gutenberg to compare the sizes of local earthquakes. It uses the size of seismic waves recorded by instruments called seismometers. Because the scale is logarithmic, a magnitude 6 earthquake shakes the ground about 10 times more than a magnitude 5.
Today, scientists mostly use the moment magnitude scale instead, because the Richter scale does not work well for very large or distant earthquakes. Moment magnitude is based on the area of the fault that slipped and how far it moved. News reports often still say Richter scale, but the numbers usually come from the moment magnitude method.
How big can earthquakes get?
Earthquakes below magnitude 3 are rarely felt. Magnitude 7 and above can cause major damage. The largest earthquake ever recorded was magnitude 9.5, in Chile in 1960. Magnitude alone does not determine damage, which also depends on depth, distance and building quality.
Did You Know?
A separate scale, the Modified Mercalli Intensity scale, describes how strongly an earthquake was felt and the damage it caused at a particular location.