seismogram

Chapter 3. Earthquakes

seismogram

After reading the chapter and attending all lectures and viewing the films, you should be able to:
1. define an earthquake; how does it differ from a seismic wave?
2. discuss the elastic-rebound theory of the cause of earthquakes. Be sure to include such terms as stress, strain, shear stress, and tension.
3. distinguish between an earthquake's focus and epicenter.
4. using the analogy of a spring (Slinky) and a rope, contrast the way in which seismic energy is transmitted through body waves.
5. distinguish between body (i.e., primary and secondary waves) and surface waves.
6. give a general explanation for how a seismograph works. 
7. distinguish between a seismograph and a seismogram.
8. explain how seismic data from three recording stations is required to pinpoint the epicenter of any earthquake on earth.
9. explain how the Richter magnitude scale is used and how it differs from the Modified Mercalli Scale of intensity. What types of information are required to calculate each of these?
10. explain why the Richter scale is logarithmic.
11. use a seismogram to calculate the magnitude of an earthquake when given the difference of arrival times of P and S waves and the amplitude.
12. discuss the relationship between magnitude and the amount of energy released by an earthquake.
13. explain the relationship between earthquakes and plate tectonics theory.
14. distinguish between foreshocks and aftershocks.
15. use the New Madrid, Mo earthquake of 1811-12 to explain the occurrence of intraplate earthquakes
16. suggest several other possible causes of earthquakes not directly related to plate tectonics theory.
17. describe to a non-scientific friend why earthquake prediction is still more art than science.
18. compare and contrast the following schools of earthquake prediction: seismic gap studies,  recurrence studies, and precursor studies 
19. design a set of procedures to be followed to minimize earthquake damage in Los Angeles; contrast it to the set of procedures you would recommend for this area.
20. explain why the term tidal wave is a misnomer and why tsunami or seismic sea wave is a more appropriate descriptor for this phenomenon.
 
Critical Thinking Questions and Activities: 
1. Via the internet, contact the USGS or any other link which can provide real-time seismographic data of epicenters, magnitudes, aftershocks, etc.
2. What is the seismic risk here at Keystone College? At your home? How safe or unsafe is the building in which you are currently living? attending classes? your home? 
3. Do you think you would be safer in a 7.0 magnitude earthquake in Los Angeles or in NEPA?
4. With information provided to you, plot the location (by latitude, longitude, and depth of focus) of the epicenters of earthquakes of the last decade. Classify earthquakes into three depth ranges (shallow = <100 km, intermediate = 100-200 km, and deep = >200 km); use a different color to map each depth range.
5. Prepare an hypothetical news release describing the cause and results of a 7.0 magnitude earthquake in your area. Be sure to describe it in terms understandable to the newspaper-reading pubic.
Resources: 
Ansfield, V. 1992. A Graphic Representation of the Richter Scale. Journal of Geological Education : 40: 381-384.
Barker, G. 1987. Interfacing the Lehman Seismograph with an Apple Computer. Journal of Geological Education : 35: 126-129.
Harden, D. 1990. An Introductory Geology Exercise on Contouring Intensities for the 1989 Loma Prieta Earthquake. Journal of Geological Education : 38: 105-106.
Johnson, A. and L. Kantner. 1990. Earthquakes in stable continental crust. Scientific American 262 (March): 68-75.
Kerr, R. 1993. Parkfield Quakes Skip a Beat. Science 259 (19 February): 1120-22.
Kroll, R. 1987. Construction Modifications of the Lehman Seismograph. Journal of Geological Education : 35: 124-125.
Lehman, J. 1977. Practical Seismograph Tracks Tremors. Science Teacher 44 (8): 43-45.
Lumsden, D. 1990. An Earthquake Lab for Physical Geology. Journal of Geological Education : 38: 30-37.
Shea, J. 1991. A Computer-based Subduction-zone Earthquake Exercise for Introductory Geology classes. Journal of Geological Education : 39: 388-392.
U.S. Geological Survey Staff. 1990. The Loma Prieta, California earthquake: An anticipated event. Science 247 (January): 286-93.
Walker, J. 1979. How to Build a Simple Seismograph to Record Earthquake Waves at Home. Scientific American 241: 152-161.
Wesson, R. and R. Wallace. 1985. Predicting the next earthquake in California. Scientific American 252 (February): 35-43.
Field Trip Opportunities: 
1. Visit the Lamont Doherty Earth Observatory in Palisades, NY. They hold an open house every spring.