Planet X Module 4. Foundation Soils

Target Level Year 8 – 12.

Rationale

Earthquake activity on active faults and in active seismic zones determines the area’s seismic hazard. Seismic hazard is enhanced in locations prone to ground failure. Seismologists and soil engineers evaluate foundation soil for this characteristic using geophones, seismic probes, and soil sampling. The resulting data are interpreted to evaluate seismic hazard and contribute to hazard maps. Hazard maps are used in defining zones for building codes that help reduce the risk of damage should an earthquake occur. This exercise simplifies this procedure using generated data from Planet X, a fictitious colony.

Focus Question

Does foundation soil affect seismic hazard?

Objectives

Students will:

1. Observe the effect of shaking on different foundation soils.

2. Evaluate two sites for seismic hazard using maps and data.

3. Choose best site for a city based on the above assessment.

Materials Needed

1. See Shake Table Activity

2. Copies of Foundation Soil Activity

Organization

1. Begin with discussion of Mexico earthquake of September 19, 1985 focusing on concentration of damage in old lake zone of Mexico City, (see figure 3. in Foundation Soil Activity.) Give geological information about city.  Ask students for possible reasons for the difference in damage between old lake zone and surrounding higher ground.  

2. Use Shake Table Activity to show the different effects of shaking in different foundation soils. This activity can be used a demonstration or if there is enough time as a student activity.

3. Introduce Planet X scenario and divide into small groups with the task of evaluating two possible city sites.  Students evaluate seismic hazard, choose location and name city. Are all groups in agreement? 

4. As an extension ask students to think of ways of reducing the risks of ground failure in liquefaction prone, seismically active areas.

This is a link to FOUNDATION SOIL ACTIVITY

SHAKE TABLE ACTIVITY

Reference Data

Site 1 is located near a transform plate boundary with a high occurrence of earthquakes. The site 1 area has a sandy, loose soil that amplifies surface seismic waves. Because the area is low-lying and may be water saturated, it is thus prone to liquefaction during an earthquake.

Site 2 is located away from the plate boundary. It has rocky and solid subsoil without porous sands. Although this site is low-lying it is not prone to liquefaction.

Site 2 is the best location for the Planet X capital city.

Core Curriculum Standards Met

Topic 1. Inquiry, Process and Problem Solving.

Topic 8. Composition of the Earth.

Topic 18.  Formation of Earth’s features

References

BOLT, Bruce A., Earthquakes, W.H. Freeman and Company, New York, NY, 1999

Related Web Sites

http://lahr.org/john-jan/psn/psn.html

This site has information on building and using shake tables.

http://mceer.buffalo.edu/education/exercises/soil.aspThe Multidisciplinary Center for Earthquake Engineering and Research site with a related teaching module.

www.cen.bris.ac.uk/students/eqteach97/

This University of Bristol site is easy to navigate and has good information and graphics.

www.eas.purdue.edu/~braile/educindex/educindex.htm

This site has links to great hands-on activities for earthquake science.

htpp://geology.usgs.gov/pdf/planet.pdf

Download “This Dynamic Planet” (T. Simkins and others.) here or order a copy of the map from US Geological Survey, Box 25286, Denver, CO. 80225. for $7 + $5 shipping.

htpp://pubs.usgs.gov/publications/text/dynamic.html

“This Dynamic Earth, The Story of Plate Tectonics”, is a companion text to the above map.

www.seismo.unr.edu/htdocs/abouteq.html

“About Earthquakes” has links to an excellent collection of lectures.