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How to Convert a Measurement on the Richter Scale

The Richter scale, created by Charles F. Richter in 1935, is a metric that measures and compares the magnitude of earthquakes. The Richter magnitude is expressed as a positive decimal number, based on the magnitude of the earthquake's largest seismic wave. A Richter magnitude of 2.0 corresponds to a very small, nearly imperceptible earthquake. The largest recorded earthquake had a magnitude of 9.5 on the Richter scale. Though this scale is often convenient, you may have reason to convert a Richter magnitude into other units for calculation or comparison.

Things You'll Need

Calculator

Instructions

- 1
  Ascertain the Richter scale magnitude. This value will be a positive decimal number -- call this number R. There is no upper limit to the Richter scale, so earthquakes could conceivably obtain a Richter magnitude of 10 or higher. For an example, an earthquake with Richter magnitude 2.0 would mean R=2.
- 2
  Multiply 1.5 times the Richter number R. The value 1.5 is just a scaling factor based on the equation defining the Richter scale. With our example earthquake, this gives 1.5*2 = 3.
- 3
  Add 4.8 to the result from step two. This represents the magnitude of a moderate earthquake which serves as a reference point for the Richter scale. Continuing the example above, 4.8+3 = 7.8.
- 4
  Raise 10 to the power of the result from step 3. The exponent in this step reverses the logarithm on which the scale is based. Because the Richter scale is logarithmic, each whole number increase in magnitude corresponds to 10 times the strength. In our example, we calculate 10 with an exponent of 7.8 to get 63,095,734.4
- 5
  Append the units, which are joules. The Richter scale roughly measures the energy of an earthquake based on its largest seismic wave. Joules are the standard unit of energy in scientific units. The energy contained in the example earthquake is 63,095,734.4 joules.
- 6
  If you wish to convert to other units of energy, simply find the conversion factor from joules to your units. For instance, you may elect to measure the earthquake by tons of TNT. The energy in a single ton of TNT is 4.184 time 10 billion joules. Dividing the example earthquake's energy in joules by this value yields about 1/100th of a ton of TNT; a small earthquake.

Nature