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The Richter Scale
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Film summary
Why the magnitude of earthquakes, measured on the Richter scale, increases so quickly – because the scale is logarithmic.Transcript
Although we only feel the most severe earthquakes, they occur across the planet every day, transmitting seismic waves through the Earth.
Their energy can be quantified using the Richter Magnitude Scale.
On the Richter scale, anything below 2 is undetectable to the average person, but earthquakes measuring 6 can wreak havoc.
The difference between 2 and 6 on this gentle curve may not seem so significant, but the Richter scale is logarithmic.
Every number on the scale represents 10 times more power than the last.
Logarithms
The Richter scale is based on powers of 10, which can be expressed using standard form notation.
1000 is 10 multiplied by 10, multiplied by 10, and can be written as 10 to the power of 3.
This is called an exponential expression.
Exponential expression
The base number, x, is raised to the power, n – which indicates the number of base numbers that are multiplied together.
Logarithms are simply the inverse of exponentials.
This logarithmic equation asks – what power is 10 raised to, to get 1000?
The answer is 3.
The Richter scale is a base 10 logarithmic scale, so each number on the scale represents a power of 10.
This means that an earthquake measuring 8 is 10 times stronger than one measuring 7, and 1 million times stronger than one that measures a 2.
Thankfully, the number of earthquakes decrease exponentially as the scale increases.
On average, only 18 earthquakes a year measure a 7 on the Richter scale.
Whereas around a thousand quakes of magnitude 2 shake the Earth every day.
