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Overview:
In this activity, students will delve into seismology—the study of earthquakes—learning about and contrasting two scales used by seismologists to categorize and compare these quaking forces of nature. Students will review firsthand accounts from people who experienced an earthquake, then employ one of these scales to categorize and map the earthquake's intensity. This activity might productively be conducted either before or after viewing the giant screen film Forces of Nature.
Connections to the Curriculum:
Geography, earth science
Connections to the National Geography Standards:
Standard 1: "How to use maps and other geographic representations, tools, and technologies to acquire, process, and report information from a spatial perspective"
Standard 7: "The physical processes that shape the patterns of Earth's surface"
Standard 15: "How physical systems affect human systems"
[Note: This lesson also conforms to National Science Education Content Standard E (Science and Technology: Understanding about science and technology) and Standard F (Science in Personal and Social Perspectives: Natural and human-induced hazards) for grades 9-12.]
Time:
Two hours
Materials Required:
- Computer with Internet access
- A variety of colored pencils
- Photocopies of the following (one copy of each for each student):
[Note: The handouts are in PDF format. Download a free copy of Adobe Acrobat Reader if necessary.]
Objectives:
Students will
- apply Modified Mercalli Intensity (MMI) values to written descriptions of an earthquake;
- map MMI values on a large-scale zip code map and defend their decisions;
- compare their MMI maps to USGS map of MMI values, noting similarities and differences; and
- explain how measures of magnitude and intensity are applied to earthquakes.
Geographic Skills:
Asking Geographic Questions
Acquiring Geographic Information
Answering Geographic Questions
Analyzing Geographic Information
S u g g e s t e d P r o c e d u r e
Opening:
Ask students if they've ever been startled in their sleep—"jolted" awake. Some people who've been sleeping when an earthquake struck weren't sure whether they were waking up naturally or experiencing a real earthquake. Others had no doubt about the nature of the jolting event.
Tell students they are going to study and compare the size, intensity, and destructive power of earthquake "jolts," as seismologists do. Seismology—from the Greek seismos, which means "shock" or "earthquake"—is the science that deals with earthquakes and other artificially produced vibrations of the Earth. Scientists such as geophysicist Dr. Ross Stein, featured in the giant screen film Forces of Nature, study earthquakes in the attempt to better predict them.
Development:
Tools called seismographs record an earthquake, and the value of its magnitude is determined using the recording and a mathematical formula. Magnitude measures the energy released by an earthquake. [Note: The Richter scale, with which students may be familiar, is one of the original scales of magnitude, but the Moment Magnitude scale, a more accurate measure of the size of the earthquake, is now preferred by seismologists.]
What other kinds of information might seismologists and others want to learn about an earthquake beyond its size in quantitative terms? (For example, what kinds of problems did the quake create for people and property? Were people hurt? Killed? Were homes or other buildings damaged?) The Modified Mercalli Intensity scale (MMI), used in the U.S., is a more subjective, qualitative measure of an earthquake's effects. The MMI value assigned depends on vibrations experienced by people in an earthquake, and by the amount of building damage done.
Have students go online to compare magnitude and intensity. Then ask them to explore different ways of measuring earthquakes. As a class, discuss how the different methods rate and describe earthquakes. Which way of measuring—by magnitude or by intensity—seems more useful? Why?
Ask students what other factors might contribute to an earthquake's effect. (The type of underlying rock or soil affects damage. Areas underlain with solid bedrock typically "ride out" earthquakes with less damage than areas with soft, unconsolidated sediments. Students can go online to learn about "Soils and Earthquakes.")
Give each pair or group a copy of Handout 1: Zip Code Base Map for the Northridge, Calif., Earthquake, January 17, 1994; a copy of Handout 2: Earthquake Experiences; and a description of the MMI scale. Explain that the magnitude of the Northridge earthquake measured 6.7, but its effects varied throughout the region. Students will analyze responses from people who experienced the quake, then determine on a map the locations of respondents.
Ask students to do the following:
- Color in the boxes of the "Intensity" key at the bottom of the map using increasingly darker colors or shades for higher intensity values (this will result in an easier map to interpret).
- Read the "Earthquake Experiences." Assign an MMI rating (I–X+) to each experience.
- Using the appropriate color for the degree of intensity, color the zip code regions on the map with the MMI rating their group assigned to each earthquake experience. (A region can have more than one MMI rating.)
- Title the map. Analyze the patterns of earthquake intensity on the map, and write observations below the map.
Closing:
As a class, discuss differences in the maps. Did groups rate some experiences differently on the MMI scale? Why? Do some color keys work better than others in depicting the intensity pattern? Ask students if they were able to determine the earthquake's epicenter. If so, how? Give students Handout 3: USGS-defined MMI Values for the Northridge, Calif., Earthquake, January 17, 1994. How does that map—with the MMI ratings determined by the USGS—compare with their maps?
Suggested Student Assessment:
Ask students what they think contributes to the different intensities of shaking that occur in different areas, but that are caused by the same earthquake. (The intensity generally decreases with distance from the epicenter. It is also influenced greatly by the type of underlying material—soft sediments shake more than hard rock.)
Ask students to agree or disagree—in writing—with the following statement: "An earthquake has one magnitude, but many intensities."
Evaluate students' work based on the amount of detail and accuracy in oral and written presentations and on the use of research. Students should show that they have
- matched MMI values to descriptions of earthquake events;
- created a map based on the interpretation of MMI data and be able to defend decisions for placement of MMI values;
- compared their own MMI maps to the USGS map with actual MMI data, noting similarities and differences; and
- explained how magnitude and intensity scales are applied to earthquakes, speculating on how similar intensity and magnitude of an earthquake impacts locations differently.
Extending the Lesson:
This lesson was adapted from an activity by Lisa Wald of USGS.
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