Like the Richter magnitude scale

Obsolete? The Richter scale is historically important, but in modern usage has been replaced by moment magnitude [0].

As others have pointed out, in any case this subjective scale has more in common with the Mercalli intensity scale [1].

[0] http://en.wikipedia.org/wiki/Moment_magnitude_scale

[1] http://en.wikipedia.org/wiki/Mercalli_intensity_scale