Alg 2 Honors – Logarithms 03
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Geologists used to use the Richter scale for the strength of an earthquake. The strength, W , of the seismic
waves of an earthquake are compared to the strength, W0 , of the seismic waves of a standard earthquake.
The Richter scale rating, M , is
W
M = log
W0
1. In 2013 the Khash earthquake in Iran had a Richter scale reading of 7.8. How many times more
powerful were the seismic waves of the Khash earthquake than standard seismic waves?
2. In 1986 the worst nuclear power plant accident in history occurred in Chernobyl, Ukraine. The explosion resulted in seismic waves with a Richter scale rating of 3.5. How many times stronger were the
seismic waves of the Chernobyl disaster than standard seismic waves?
3. Let M1 and M2 be the magnitudes of two earthquakes whose seismic waves are of sizes W1 , and W2 ,
respectively. Using log properties, find a simplified formula for the difference M1 − M2 in terms of W1 ,
and W2 .
4. The 2010 earthquake off California had a rating of 7.2 on the Richter scale. How many times larger
than the California earthquake were the seismic waves in the March 2005 earthquake off the coast of
Sumatra, which measured 8.7 on the Richter scale?
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