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Compare the Magnitudes of Earthquakes

Calculator for the comparison of two Earthquake magnitudes given in the Richter. The Richter scale is the publicly most well known scale to measure earthquake magnitudes. This is a logarithmic scale, where each step has ten times the power of the previous one. So an earthquake that registers 7.5 is 10 times stronger than one with 6.5. The moment magnitude scale is far more complicated, but more suitable for stronger earthquakes.
Please enter two values, the third will be calculated.

First value (a):
Second value (b):
Ratio a to b:

Round to   0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15   decimal places.

Example: an earthquake that registers 4 on the Richter scale makes the furnishings shake. An earthquake that registers 9 is a hundred thousand times stronger (10^9-4 = 10⁵ = 100000). With 9.5, this is more then three hundred thousand times stronger.

The Richter scale was developed in 1935 at the California Institute of Technology by Charles Francis Richter, after whom it was named, and Beno Gutenberg. It uses values ​​taken a few hundred kilometers from the epicenter of the earthquake. The current state of measurement technology, however, is that earthquake measuring devices are distributed all over the world, and all of their data is used to determine earthquake strength if they can provide relevant data. For this reason, strengths are now more often determined using the moment magnitude scale, but the Richter scale is still mentioned often in the news. For earthquakes up to a magnitude of 6.5, both deliver almost identical values. After that, the moment magnitude scale is more precise and delivers values ​​that are about 0.2 to 1 higher. This is a very relevant difference, because one step difference, as occurs in strong earthquakes, means ten times the energy.
The world's strongest earthquake ever recorded so far, in 1960 in Chile, registered a magnitude of 9.6 on the moment magnitude scale. The Richter scale would register only 7 to 8 here.

Last updated on 10/05/2025. Author: Jürgen Kummer

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