1906 vs. 1989: A Comparison of Two Major Earthquakes

Materials / Preparation

• Computers with internet access
• A copy of Comparing Two Earthquakes worksheet for each student
• LCD projector to project the maps for Activity 1 or create an overhead for the maps. Either choice will allow you to guide the students through the activity
• Large paper for students to post their hypotheses

Grouping

Whole class and then pairs or groups of four, depending on computer availability

Teacher tips

Preview the assignments before assigning to students:

• Comparison of 1906 and 1989 earthquakes: Because students will be comparing two earthquakes, it will be important that they understand the information presented to them. We recommend that you go through all of the information together for one of the two earthquakes and then have them make the comparisons between the two earthquakes.
• Seismological Exercises: Students will need to scroll down to section two. Preview the entire lesson, you may choose to have students do more than section two, however for the purpose of this lesson, we will refer only to section two.
• An answer sheet for the Comparing Two Earthquakes worksheet is available.

Procedures

1. Class discussion:
   
   a. Review with students that earthquakes are a sudden release of energy along a fault and that this energy is released in waves. We feel shaking as these waves move through the earth beneath our feet.
   
   b. Do all areas experience the same amount of shaking? What do you think would determine the amount of shaking? Make a list of the students’ ideas on the board.
   
   c. Tell students they will be exploring information about earthquakes to determine how well their ideas are supported by the evidence.
   
2. Project the Comparison of 1906 and 1989 earthquakes website. Note: This site can be accessed directly from the Earthquake Hazards Student Web Page. Demonstrate all of the features pertaining to the 1989 earthquake (see Teacher Tip) as a group.
   
   a. Enlarge the 1989 map (left-hand map, click to zoom or use zoom buttons)
   
   b. Discuss with class what the map shows. What do the different colors indicate?
   
   c. Return to the main page (use the Back arrow on browser) and project the 1906 map. How does this map differ? Point out the topographic features – bay, coastal mountains, central valley.
   
   d. Compare the California Maps with the Bay Area View Map. Using the map legend at the bottom of the Bay Area View maps, discuss the meaning of the different colors. Make sure that students understand that the different colors represent different levels of intensity, which can be labeled by using either Arabic numerals 1 - 10+ or Roman numerals from I to X+. Instrumental intensity is designed to be equivalent to the Modified Mercalli scale. They are used interchangeably on this web site, but it is probably best to teach the name as Modified Mercalli Scale.
   
   Tell them to look at a yellow section of the legend. What word is used to describe the perceived shaking? The potential damage? Point out the cities they are to find, Santa Rosa, Sacramento, and Oakland.
   
   d. Return to the main page and move to the next map, labeled Animation. Demonstrate how the animation flips between the two earthquakes they will be comparing and that it is important to watch the map several times.
   
3. Hand out the Comparison of Two Earthquakes worksheet to each student. Have them break into pairs and move to a computer. Instruct students to follow the steps on the worksheet. Advise them that they can access the website directly from the Earthquake Hazards Student Web Page. Check to make sure students are at the correct site and that they are able to navigate correctly and can enlarge the maps.
   
4. Once they are finished, discuss with students their explanations/hypotheses on what determines intensity. What influences the amount of shaking felt at a given location during an earthquake? Guide the discussion so that students realize the importance of the earthquake's magnitude and the distance from the fault.
   
5. Tell students that in the next activity they will continue to explore and gather further information that may or may not support their hypotheses.

Resources used

Comparison of 1906 and 1989 earthquakes
http://www.teachingboxes.org/catalog.jsp?id=DLESE-000-000-009-322

Seismological Exercises
http://www.tulane.edu/~sanelson/geol204/eqexercises.htm