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# frequency - SSAC2006.QE531.LV1.6 Frequency of Large...

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1 Earthquakes with a magnitude 7 to 7.9 are considered major earthquakes. Earthquakes with magnitude larger than 8 are considered great earthquakes. How frequently do these large earthquakes occur? SSAC2006.QE531.LV1.6 Frequency of Large Earthquakes Introducing Some Elementary Statistical Descriptors Prepared for SSAC by Len Vacher – University of South Florida © The Washington Center for Improving the Quality of Undergraduate Education. All rights reserved. xxxx Supporting quantitative concepts/skills Mean, median, mode Variance, standard deviation Percentiles, Quartiles Interpolation Normal distribution Core Quantitative Issue Data analysis: Exploratory statistical descriptors

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2 Preview The mission of the U.S. Geological Survey National Earthquake Information Center (USGS NEIC) is “to determine rapidly the location and size of all destructive earthquakes worldwide and to immediately disseminate this information to concerned national and international agencies, scientists, and the general public” ( End note 1 ). The NEIC now locates some 50 earthquakes a day, or about 20,000 per year Slide 3 gives some background on earthquake frequency and magnitude. Slide 4 presents the 30 years of data that you will study: the number of large earthquakes per year for 1970-1999. Slides 5-9 ask you for the mean; the variance and standard deviation; the maximum, minimum and range; the modes; and the median and quartiles of the data. Slides 10 and 11 look at the quartiles more closely – in terms of percentiles. Linear interpolation becomes relevant in Slide 11 . Slides 12-14 ask you to plot the percentiles. In particular, Slide 14 asks you to consider the distribution of the data. How does the relation between the key percentiles and the standard deviation compare to that of the normal distribution? Slide 15 wraps up, and Slide 16 gives you the end-of-module assignments, which involve data from 1940-1969.
3 Background on earthquake magnitude and frequency B C D E F G H I 2 Magnitude 2000 2001 2002 2003 2004 2005 2006* 3 4 8.0 to 9.9 1 1 0 1 2 1 0 5 7.0 to 7.9 14 15 13 14 14 10 9 6 6.0 to 6.9 158 126 130 140 141 144 104 7 5.0 to 5.9 1345 1243 1218 1203 1515 1699 1140 8 4.0 to 4.9 8045 8084 8584 8462 10888 13917 9736 9 3.0 to 3.9 4784 6151 7005 7624 7932 9173 7535 10 2.0 to 2.9 3758 4162 6419 7727 6316 4638 3014 11 1.0 to 1.9 1026 944 1137 2506 1344 26 14 12 0.1 to 0.9 5 1 10 134 103 0 2 13 No Magnitude 3120 2938 2937 3608 2939 867 541 14 15 Total 22,256 23,534 27,454 31,419 31,194 30,475 22,095 16 17 Deaths (estimated) 231 21,357 1685 33,819 284,010 89,354 6595 U.S. Geological Survey National Earthquake Information Center, 11/6/2006 To appreciate the size of the large earthquakes, remember this: A magnitude-8 earthquake releases about 32× as much energy as a magnitude-7 earthquake, and a magnitude-7 earthquake releases about 32× as much energy as a magnitude-6 earthquake. Therefore a magnitude-8 earthquake is about 1000× as strong as a magnitude-6 earthquake. ( End note 3

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frequency - SSAC2006.QE531.LV1.6 Frequency of Large...

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