Measuring Earthquake Magnitude & Energy: Richter vs. Moment Magnitude Scale

EarthquakePhoto byShefali LincolnonUnsplash

When most people hear that Washington State has had another earthquake, the first thing they often ask is how large was the earthquake? What did it rate on the Richter Scale?

Developed in 1935 by Charles F. Richter, the Richter scale was originally used to measure the magnitude of an earthquake. It was devised to measure the strength of the earthquake from as little as a .1 upwards to a 9.9 (which is exceedingly rare). The measurements also help to compare one earthquake to another.

Here’s how it works:

The Richter scale is considered a logarithmic which means that each whole number represents a tenfold increase in measured amplitude or approximately 31.6 times more energy than the previous number. Example: An earthquake that registers 5.0 has ten times the energy of a 4.0 earthquake.

Seismographs are used to measure the seismic waves that an earthquake generates. This device use instruments to draw a pattern of the peaks and valley’s of any activity. You can see a chart of the Richter scale here.

Amplitude Measurements are how the seismographs record the seismic waves. The maximum amplitude of these is used in calculating the waves in calculations. The Richter scale is accurate for the smaller earthquakes, however, it’s accuracy has been questioned in regard to larger earthquakes.

Earthquakes over 7 on the Richter scale aren’t accurately reflected, so the 1970s, The Moment Magnitude Scale was created to compare seismic moment and total energy release. It was designed to accurately measure the total release of energy by an earthquake.

Although the terms are often interchanged when discussing the “ranking” of an earthquake, the latter method is more accurate and more frequently used to discern the velocity of earthquakes today. What’s the largest earthquake you’ve been in? What did it feel like?

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