The Richter Scale
A
scale for comparing the intensities of earthquakes was devised around
1940, by a man named Charles Richter. The intensity of an earthquake
is measured by the amount of ground motion as measured on a
seismometer. The Richter scale is not designed so that you must know
the actual intensities or seismometer readings. The scale is simply
used to compare intensities according to the following rule:
Each
increase of 1 unit in magnitude on the Richter scale corresponds to a
10-fold increase in intensity as measured on a seismometer.
This
makes it relatively easy to compare the intensities of earthquakes
with a magnitude difference of integer amounts. For example, the 1976
Italy earthquake was a magnitude of 6.5, while the Guatemala
earthquake of the same year had a magnitude of 7.5, which is exactly
one unit greater. This means the second earthquake was 10 times more
intense than the first.
1) |
Calculate, using exponents, the intensity difference between a 5.5 magnitude quake and a 7.5. |
2) |
Calculate, using exponents, the intensity difference between a 5.5 and an 8.5. |
How do we compare the intensities of earthquakes that do not differ by a whole number?
We can do this by using a property of exponents. If we express the intensity I as an exponential function of the magnitude M.
We will use the Alaska and Turkey earthquakes of 1964 and 1966.
|
This represents the Alaska earthquake. And this is the Turkey earthquake. We are asked to compare intensities, so the ratio will be useful. =39.81 =approximately 40 times as intense. |
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We can also use exponents to calculate
the energy of an earthquake. The formula for the energy (in kWh,
kilowatt hours) is:
where E is the energy, and M is the earthquake magnitude.
5) |
Calculate the energy of a magnitude 8.7 earthquake. |
6) |
Calculate the energy of a magnitude 9.0 earthquake. |
7) |
Using your results from above, can you calculate how many years you would have to run a 100W light bulb to use the same amount of energy as in the 9.0 quake? |
Now that you understand the Richter scale, let's try to discover what effect the large earthquake will have on Vancouver.
BERICHTERSTATTUNG DER LANDESREGIERUNG ENTSPRECHEND § 10 THÜRINGER KINDER UND
EARTHQUAKE MAGNITUDE DISTRIBUTION THE GUTENBERGRICHTER LAW RELATES THE MAGNITUDE
FMAMITTEILUNG 122009 ANHANG 2 STANDARDBERICHTERSTATTUNG „RISIKOANALYSE PRÜFSTRATEGIE“ SEITE
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