Earthquakes and Tsunamis: For Educators and Students
Table Of Contents
EQ WEB Sites: General Interest
Basic Earthquake Science
An earthquake is the shaking of the earth that occurs after pieces of the crust of the Earth suddenly shift. The term earthquake describes the sudden slip on a fault and includes the ground shaking and radiating seismic energy that is caused by the slip. Volcanic activity, or other geologic processes, may cause stress changes in the earth that can also result in an earthquake. Earthquakes can occur anywhere in the world although some areas of the globe are more likely to experience an earthquake than others. Earthquakes occur in all types of weather, in all climate zones, in all seasons of the year, and at any time of day making it impossible to predict with any certainty when an earthquake is likely to occur. The best seismologists (scientists who study earthquakes) can do is to look at the historical record of earthquake activity for any geographical area and use this data to calculate the probability of an earthquake occurring in the future. Earthquake prediction is still in the future.
A tsunami is a series of sea waves that can be caused by earthquakes or landslides at or beneath the sea floor. The displacement of the sea floor that occurs during certain large submarine earthquakes and landslides causes displacement of large volumes of the sea water above it producing large, fast moving waves. When a coast line experiences a tsunami it can be due to an earthquake near the coast or due to a quake occurring in a distant part of the ocean. Coastal areas may experience little or no damage from an earthquake but can be devastated by the resulting tsunami.
The earth’s crust is divided into eight major pieces called plates and many minor plates. In the Pacific Northwest, there are two plates that figure importantly when considering earthquake activity in this region. The North American or Continental Plate is the plate on which the states of Oregon, Washington and California sit. The Juan de Fuca Plate is an oceanic plate that lies in the Pacific Ocean, west of the Pacific Northwest coastline. The boundary where these two plates converge is called the Cascadia Subduction Zone and lies about 50 miles offshore. As the Juan de Fuca Plate collides with the North American Plate it subducts or slides underneath it into the earth's mantle. The collision of the two plates can produce three different types of earthquakes.
A. Subduction Zone Earthquakes
When an oceanic plate gets pushed underneath a continental plate it will often stick instead of sliding smoothly. A large amount of stress builds up over time and may be released suddenly as a large earthquake. There have been no earthquakes recorded in the Cascadia Subduction Zone since records began in 1790. However, we know that Cascadia has had magnitude 8-9 earthquakes in the past, and other subduction zones have produced quakes of magnitude 8 or larger. The Alaskan Quake of 1964 is one example. If such an event were to occur the quake would be centered off the coast of Washington or Oregon where the plates converge. Such earthquakes typically have a minute or more of strong ground shaking, and are quickly followed by damaging tsunamis and numerous large aftershocks.
B. Deep Earthquakes
Deep earthquakes occur within the Juan De Fuca Plate as it sinks into the mantle. These earthquakes occur approximately 25-100 kilometers in depth. Due to their depth, aftershocks are not usually felt. History indicates that these earthquakes do not occur east of the Cascade Mountains. The most recent damaging earthquake of this type, magnitude 6.5, occurred in 1965 between Seattle and Tacoma, Washington.
C. Shallow Earthquakes
Shallow earthquakes occur within the North American Plate itself. These kinds of earthquakes are believed to be caused by stress transmitted from the Cascadia Subduction Zone into the interior of the North America plate. They generally occur at depths of 30 kilometers or less and have occurred throughout Washington and most parts of Oregon. In 1993 a magnitude 5.6 earthquake occurred in the Willamette Valley, Oregon and two earthquakes, magnitudes 5.9 and 6.0, occurred near Klamath Falls, Oregon.
Map from the University of Washington Geophysics Program WEB site at: http://www.geophys.washington.edu/SEIS/PNSN/INFO_GENERAL/eqhazards.html
III. Conclusion
The twentieth century has witnessed an increased interest in the scientific study of earthquakes. Earthquake research occurs worldwide and is especially active in the areas affected by earthquakes, including Japan, the United States, Europe, Russia, Canada, Mexico, China, Central and South America, New Zealand, and Australia, among others. If you would like to learn more about earthquakes, tsunamis and the exciting field of seismology the links below provide some of the most current information available. If you have any comments or questions about this WEB Site, please direct them to Kathy Blaustein.
IV. Earthquake WEB Sites of Interest to Educators
Earthquake Safety by the American Red Cross: http://www.redcross.org/pubs/dspubs/cdelist.html#chem Safety plans and supply kits, general disaster preparedness and information pamphlets and lessons available from the Red Cross.
Earthquakes by FEMA for Kids: http://www.fema.gov/kids/quake.htm Activity plans for teaching the younger student about earthquakes including Tasty Quake, EQ Math, games and legends.
Where Can I Find Teaching Resources About Seismology? by the UC Berkeley Seismological Lab: http://www.seismo.berkeley.edu/seismo/faq/teaching.html Organizes some of the many resources available for K-12 teachers.
Earthquakes: A Teacher’s Package for K-6: http://www.nap.edu/readingroom/books/rtmss/4.45.html An EQ curriculum available from FEMA.
Seismology Resources for Teachers by the Seismological Society of America: http://web.ics.purdue.edu/~braile/edumod/seisres/seisresweb.htm Includes a list of references, maps, slides sets and videotapes for teaching topics related to seismology.
Free Seismology Word Search Puzzle: http://freebies.about.com/library/words/blws013.htm?once=true&
Plot That Quake! By Berkeley Seismological Lab, Patricia Spencer, middle school teacher, San Francisco Unified SD and UC Berkeley Interactive University Project: http://www.seismo.berkeley.edu/seismo/istat/digiguide/EQ.html Involves students in the activities of data collection and analysis to foster questions about the how, when, where, and why of earthquakes.
Earth Science Lessons by Scott Johnson of the Volcano World development team: http://volcano.und.nodak.edu/vwdocs/vwlessons/lessons/lesson.html Includes lesson plans on plate tectonics, earthquakes and volcanoes and rocks and minerals.
Where Can I Find Teaching Resources About Seismology? by the UC Berkeley Seismological Lab: http://www.seismo.berkeley.edu/seismo/faq/teaching.html Organizes some of the many resources available for K-12 teachers.
Seismology Resources for Teachers by the Seismological Society of America: http://web.ics.purdue.edu/~braile/edumod/seisres/seisresweb.htm Includes a list of references, maps, slides sets and videotapes for teaching topics related to seismology.
Free Seismology Word Search Puzzle: http://freebies.about.com/library/words/blws013.htm?once=true&
Earthquakes: http://www.jclahr.com/science/psn/index.html John Lahr, USGS seismologist, has developed hands on projects related to earth science and seismology including table top seismology, an earthshaking lab, a model of sea floor spreading and subduction and wave demonstrations.
Big Trouble in Earthquake Country by Lawrence Hall of Science and University of California, Berkeley: http://cse.ssl.berkeley.edu/SEGwayEd/lessons/earthquake_country/5eqcountry.homepage.html Lesson plans include activities that aid students in developing a better understanding of the complex nature of the interaction between human beings and earthquakes.
When the Earth Moves: Seafloor Spreading and Plate Tectonics http://www.beyonddiscovery.org/content/view.article.asp?a=229 An excellent article by the National Academy of Sciences.
Virtual Earthquake from Geology Labs On-Line, California State University, Los Angeles: http://www.sciencecourseware.com/
An interactive Web-based program designed to introduce the concepts of how an earthquake epicenter is located and how the Richter magnitude of an earthquake is determined. Designed for high school AP level science and college.
Where Can I Find Teaching Resources About Seismology? by the UC Berkeley Seismological Lab: http://www.seismo.berkeley.edu/seismo/faq/teaching.html Organizes some of the many resources available for K-12 teachers.
Seismology Resources for Teachers by the Seismological Society of America: http://web.ics.purdue.edu/~braile/edumod/seisres/seisresweb.htm Includes a list of references, maps, slides sets and videotapes for teaching topics related to seismology.
Free Seismology Word Search Puzzle:http://freebies.about.com/library/words/blws013.htm?once=true&
Earthquakes: http://www.jclahr.com/science/psn/index.html John Lahr, USGS seismologist, has developed hands on projects related to earth science and seismology including table top seismology, an earthshaking lab, a model of sea floor spreading and subduction and wave demonstrations.
Seismic and Architectural Information for the Corvallis 509J School District: http://www2.corvallis.k12.or.us/seismic/ Results of recent seismic studies of area schools.
Earthquake Information: Reducing Hazards by the US Geological Survey: http://quake.wr.usgs.gov/ Includes maps and lists of recent earthquakes, EQ hazards and preparedness, and descriptions of ongoing research.
Department of Geosciences at Oregon State University: http://oregonstate.edu/dept/geosciences/
Information about classes, special programs and research being conducted by OSU faculty.
Earthquake Information from Humboldt State University: http://sorrel.humboldt.edu/~geodept/earthquakes/eqk_info.html Excellent source of information about seismic events and research on the north coast of California.
Frequently Asked Questions from the UC Berkeley Seismological Lab: http://www.seismo.berkeley.edu/seismo/faq/faq.html#current An extensive archive of questions in every area of seismology including a glossary, EQ measurement and EQ engineering.
The World Wide Earthquake Locator by the University of Edinburgh: http://www.geo.ed.ac.uk/quakes/quakes.html Information collected by the USGS about recent EQs is retrieved by the Locator and displayed.
Earthquakes of the Pacific Northwest, Oregon State University: http://oregonstate.edu/instruct/geo380/study-380.html A study guide for a university level course in earthquake science.
Frequently Asked Questions about Earthquakes by the USGS: http://earthquake.usgs.gov/faq/ Questions on every area of study related to earthquakes.
Oregon Dept. of Geology and Mineral Industries (DOGAMI): http://sarvis.dogami.state.or.us/ Includes information specific to western Oregon.
Earthquakes by the King County, Washington Office of Emergency Management: http://www.metrokc.gov/prepare/preparerespond/hazardsdisasters/earthquakes.aspx Information about earthquake preparedness in King County, Washington.
Current EQ Information by the USGS: http://wwwneic.cr.usgs.gov/ Includes current earthquake maps from around the world.
Pacific Northwest Earthquake Information by the University of Washington: http://www.geophys.washington.edu/SEIS/PNSN/ Information about earthquakes and tsunamis for the Pacific Northwest region.
Plate Tectonics, the Cause of Earthquakes by the Nevada Seismological Lab: http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html A graphically illustrated discussion about plate tectonics.
Questions and Answers on EQ in Washington and Oregon by University of Washington Geophysics Program: http://www.geophys.washington.edu/SEIS/PNSN/INFO_GENERAL/faq.html
Seismic Resources on the World Wide WEB by the Georgia Tech Earthquake Hazards and Recording Workshop: http://www.gpc.edu/~pgore/seismic.htm Many links to seismic WEB sites including several with instructions on building seismographs.
ABAG Earthquake Maps and Information: http://www.abag.ca.gov/bayarea/eqmaps/eqmaps.html Information about earthquakes and the hazards associated with them collected by the Association of Bay Area Governments
National Earthquake Hazards Program (NEHP) of Canada: http://www.seismo.nrcan.gc.ca/index.html Excellent information source for seismic events in Canada.