National Richter Scale Day

Richter Scale Day celebrates the birth of the inventor of the Richter Scale, Charles F. Richter, on April 26, 1900. The Richter scale assigns a magnitude number to quantify the size of an earthquake. The Richter scale, developed in the 1930s, is a base-10 logarithmic scale, which defines magnitude as the logarithm of the ratio of the amplitude of the seismic waves to an arbitrary, minor amplitude.