People like to compare things so we can wrap our minds around difficult concepts and events. For instance, there have long been means of comparing the severity of hurricanes and tornadoes. If you’ve ever experienced a tremor or a full blown earthquake, the magnitude of the shaking becomes more than a curiosity to you.
The magnitude of an earthquake is determined from the logarithm (a mathematical method of expressing ratios) of the amplitude (the range of vibratory movements measured from an average position to an extreme position) of waves recorded by seismographs.
The Richter Scale expresses magnitude in whole numbers and decimal fractions. For instance, a magnitude 4.3 shaker is a relatively mild earthquake, a magnitude 5.3 is a moderate quake, and a 6.3 is a strong earthquake. Each increase in whole numbers is a tenfold increase in amplitude. Seismologists understand that each whole number increase means the release of around 31 times more energy than the preceding numerical value.
The Richter Scale has no upper limit. However, scientists have developed another similar scale for the study of the most severe earthquakes called the “moment magnitude scale”.
As a point of clarification, the Richter Scale is not a measure of fatalities and physical damage to populated areas. The measurement applies only to the magnitude of the shock waves. For example, a 6.8 magnitude quake might destroy a city, but one of the same force in the wilderness might only scare deer and elk. The same force on the ocean floor might not even be felt by us land dwellers. That means the Richter Scale is a way of comparing earthquakes to one another.
How did the Richter Scale come about and how did it get its name? The man who came up with the idea was Ohio native Charles Richter. His family moved to Los Angeles in 1909. After young Charles graduated from Los Angeles High School, he moved to the Bay Area to attend Stanford University. There, he earned his undergraduate degree in 1920. Following that, he started work on his PhD in theoretical physics at the California Institute of Technology. However, before finishing his PhD, he accepted a position at the Carnegie Institute of Washington. That is where Richter became interested in seismology.
In 1927, Richter returned to Southern California and joined the staff of the Seismological Laboratory under the direction of Harry Wood. There, Richter did the routine work of measuring seismograms (the graphs of quakes) and the locations of earthquakes in order to compile a catalogue of epicenters and times of occurences. The study regarded seven widely spaced geological stations equipped with seismographs across southern California.
There was difficulty in ranking or comparing various earthquakes with one another. Eventually, Richter’s colleague Dr. Beno Gutenberg suggested that amplitudes be plotted logmarithmically. So, Richter set about to plot the seismographic waves on a graph. The differences formed a new instrumental scale that contrasted with the intensity scale.
This new scale measured comparative magnitude. Richter’s boss, Harry Wood, insisted that the new scale should be given a distinctive name, so Richter simply named it after himself.
There was still a need to apply the Richter scale to events outside of Southern California and the particular types of seismographs had been used. In 1936, Richter again collaborated with Dr. Gutenberg. Together, they calibrated the scale to apply universally to all areas on Earth.