<p>The Richter Scale</p><p>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: </p><p>Each increase of 1 unit in magnitude on the Richter scale corresponds to a 10-fold increase in intensity as measured on a seismometer. </p><p>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.</p><p>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. </p><p>How do we compare the intensities of earthquakes that do not differ by a whole number?</p><p>We can do this by using a property of exponents. If we express the intensity I as an exponential function of the magnitude M.</p><p>We will use the Alaska and Turkey earthquakes of 1964 and 1966.</p><p>This represents the Alaska earthquake.</p><p>And this is the Turkey earthquake. </p><p>We are asked to compare intensities, so the ratio will be useful.</p><p>=39.81 =approximately 40 times as intense. </p><p>3) Calculate the intensity difference between a 5.5 and a 6.2 magnitude earthquake. 4) Calculate the intensity difference between an 8.5 and a 2.7 magnitude aftershock. The Richter Scale</p><p>We can also use exponents to calculate the energy of an earthquake. The formula for the energy (in kWh, kilowatt hours) is: </p><p> where E is the energy, and M is the earthquake magnitude.</p><p>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? </p><p>Now that you understand the Richter scale, let's try to discover what effect the large earthquake will have on Vancouver.</p>