There are two major ways to measure an earthquake effect, of which two different apparatus are used for the measurements. You can measure an earthquake based on the magnitude of seismic energy, or based on the intensity, that is the effects it has on the surrounding. So, the appropriate barometer used while measuring based on the seismic energy magnitude is the Richter scale, while the barometer used for measuring based on the intensity or quake effect is the Mercalli scale.
These two scales are popularly used in the United States. However, there are other scales that can be used in substitute for the Mercalli scale, such as the MSK scale, Shindo scale, EMS scale, and the INQUA scale. The Mercalli scale, which is fully referred to as the Modified Mercalli Scale, has been since the 19the century and is older than the Richter scale. Charles Richter, with an assist from Geno Gutenberg, developed the Richter scale in the year 1935.