The Richter scale, which measures the magnitude of earthquakes, was developed in 1935 by Charles F. Richter at the California Institute of Technology. The magnitude is determined by readings of the seismic waves resulting from the earthquake's vibrations. For example, microearthquakes -- not generally felt by humans -- register about 2.0 or less on the Richter scale. With every whole point the magnitude rises, the strength of the waves increases tenfold. A temblor with a magnitude of 8.0 or more is considered a "great earthquake."
The Richter scale doesn't measure quake damage; this is dependent on a variety of factors including population at the epicenter, terrain, depth, etc.
Also Known As: earthquake magnitude scale