Written by: on April 26, 2021 @ 8:00 am

Join High Touch High Tech in celebrating
Richter Scale Day
April 26th!

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National Richter Scale Day – April 26

Does the name Charles F. Richter mean anything to you? Is he your friend on Facebook or Instagram? Is he a YouTube Star? No! Back in 1935, 86 years ago, this man developed a mathematical way to determine the strength of earthquakes!

Image Source: Wikimedia Commons
Charles Richter

You may have heard the term “Richter scale”, but the official name is Richter Magnitude scale. Charles Richter was working at the California Institute of Technology and developed a mathematical device to compare the size of earthquakes. Trying to determine the strength of earthquakes is no easy task. In fact, it is extremely complicated and requires serious math.

The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included for the variation in the distance between the various seismographs and the epicenter of the earthquakes. The epicenter is where the earthquake first began. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. 

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1906 San Francisco Earthquake Seismograph

For example, a magnitude 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value. Amazing!!

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Richter scale seismic activity diagram with shaking intensity, from moving furniture to crashing buildings.

Richter was born in Overstock, Ohio.  He grew up with his maternal grandfather, who moved the family to Los Angeles in 1909. After graduating from LA high school, he attended Stanford University.  In 1928, he began work on his PhD in theoretical physics from the California Institute of Technology, but, before he finished it, he was offered a position at the Carnegie Institute of Washington.

He became fascinated with seismology (the study of earthquakes and the waves they produce in the earth). Thereafter, he worked at the new Seismological Laboratory in Pasadena, California under the direction of Beno Gutenberg.

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Beno Gutenberg

 In 1932, Richter and Gutenberg developed a standard scale to measure the relative sizes of earthquake sources, called the Richter scale. In 1937, he returned to the California Institute of Technology, where he spent the rest of his career, eventually becoming professor of seismology in 1952.

Richter chose to use the term “magnitude” to describe an earthquake’s strength because of his early interest in astronomy; stargazers use the word to describe the brightness of stars.

Gutenberg suggested that the scale be logarithmic so an earthquake of magnitude 7 would be ten times stronger than a 6, a hundred times stronger than a 5, and a thousand times stronger than a 4. (The 1989 earthquake that shook San Francisco was magnitude 6.9.)

Image Source: Wikimedia Commons
Iceland Earthquake March 7, 2021 – Magnitude 5.2

The Richter scale was published in 1935 and immediately became the standard measure of earthquake intensity. Richter did not seem concerned that Gutenberg’s name was not included at first; but in later years, after Gutenberg was already dead, Richter began to insist for his colleague to be recognized for expanding the scale to apply to earthquakes all over the world, not just in southern California. Since 1935, several other magnitude scales have been developed. But it is the Richter scale that remains the standard.

Interested in becoming a seismologist for the day? Create your own earthquake with our at-home experiment, Shaker Table. Test the magnitude of your earthquake and give it a rating from the Richter Scale!

Lesson Plan:

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