Earthquake Magnitude

Earthquake magnitudes are generally measured using either one of the two different scales: Richter scale and Mercalli (intensity) scale

Richter scale:

• logarithmic scale (goes up by "X10" eg. magnitude 4.0 is *10 of magnitude 3.0)
• Only has one measurement per earthquake
• Scientific
• Use seismometers
• Scale from 0-10

Mercalli scale:

• Measured on a scale from I - XII the intensity of an earthquake
• Measurement varies from area
  • may have more than one value for one earthquake
  • **subjective**
• Based on effect of earthquake on nature, buildings etc.
• Measures damage / impact

Differences between the two scales

The Richter scale and the Mercalli scale are different in many ways. While one measures magnitude based on information from seismometers, the other is more subjective and is based on what people feel(observational) and their observations of damage to buildings.

Since the effect of an earthquake vary from place to place, one earthquake may have several different readings on the Mercalli scale. However, one earthquake only has one magnitude and there will only be one reading on the Richter scale.

The scales are also very different. The Richter scale goes up to 10, but is a logarithmic scale, making it harder for the public to understand. Unlike the Richer scale, the Mercalli scale goes from 1-12 and since it is a measure of intensity, it is a lot easier for the public to understand the damage an earthquake brought to an area.

The main difference between the Richter scale and the Mercalli scale is that one is more scientific and the other is more subjective.