Exploring a Current Earthquake

Students explore data for a recent earthquake, recording observations about where the earthquake occurred, where ground motion was recorded, and where it was felt.

Materials / Preparation

• Access to the internet
• Student computers with access to internet (optional)
• LCD Projector
• Rapid Earthquake Viewer (REV)
• A recent earthquake
• Poster size map of the world and small hand out maps for plotting locations if working in small groups
• Student worksheet
• World Map
• ShakeMaps

Grouping

This activity begins as a class discussion followed by small group (or individual) work to explore the earthquake data. Directions are also provided to explore the data as a class.

Teacher tips

Before class, go to the Rapid Earthquake Viewer (REV) to choose a recent earthquake for this activity. If you have time, find a photo of the area, perhaps from a news article. A good online tool is the Earthquakes Headlines from IRIS. While any earthquake will work for this exercise, selecting a larger earthquake that has occurred on or very near land will provide more descriptive shake maps. Middle school students may require additional guidance in navigating and interpreting the ShakeMaps site.

Procedures

1. Initiate a class discussion regarding a recent earthquake by asking students if they are aware of the event and what they have heard about it. Display a photograph of the area from a news article to gain their attention. Some questions to ask:  How would you go about finding more information about the earthquake?  What kinds of information do scientists gather about earthquakes and what does it tell them? Students may mention seeing or reading about the earthquake via TV/the internet/newspaper; guide students to become aware of primary sources such as REV, IRIS and USGS. Students may also concentrate on the destruction caused by an earthquake. The latter portion of this activity provides an exploration of the shaking (and potential damage) from an earthquake.
   
   
2. Using a projector, go to REV. Recent earthquakes are listed on the left hand side of the page. Point out which earthquake the class is investigating.
   
   
3. Ask your students where the earthquake occurred. Ask:  Are you familiar with this area of the world?
   
   
4. Click on the link to take you to the Earthquake info page for this event. On the left you will see a small world map with a circle on it that is centered on the epicenter. The latitude and longitude of this location is provided.  Ask students to plot this on the classroom poster-map or on their individual maps to visualize a more specific location at a larger scale.  In what country / state did the earthquake occur? What cities are near by? 
   
   
5. Ask: What other data is provided about the earthquake on this page? This offers an opportunity to discern what students currently know about earthquake terminology. Explain that the latitude and longitude on the map represents the epicenter, a point on the surface of the Earth directly above the point within the Earth where the earthquake began, called the focus.  Click on the text “Depth” to view a glossary entry for this term. Follow the link to the term “focus” to clarify the distinction between the epicenter and the focus of an earthquake. You may choose to offer more detail on faults and plate boundaries if at an appropriate point in your curriculum and time allows.
   
   
6. Go back to the Earthquake Info page by using your browser’s back button twice and have the students examine the seismograms that are displayed for this earthquake. The squiggly lines in the seismograms capture the amount of ground shaking that occurred at different stations located at different distances from the earthquake epicenter. [Note: distances are provided in degrees from the earthquake. 10 degrees is approximately 111 kilometers distance on the surface of the Earth. Also note that the scale of the seismograms recorded farther away from the earthquake have been adjusted so that you can see some general detail about the earthquake.]
   
   
7. The stations are listed in the bottom portion of the page. Ask: How many stations are shown here?  What is the range of distances from the epicenter?
   
   
8. Click on the station code for the closest one to the earthquake location. Describe to the students: Three seismograms are shown. Ground motion can be measured in 3 directions – up and down or vertical, and laterally in both a North-South axis and East-West axis. The size of the amplitude indicates how vigorous the shaking was, and is measured as a velocity in microns/sec, mm/sec or nm/sec.  Time since the earthquake occurred is measured in hours:minutes:seconds on the x-axis and indicates how long since the earthquake began that ground motion was detected at this station.
   
   
9. Have students work in groups of two to explore this earthquake further. Have students’ select 4-5 stations at a variety of distances and plot each location’s lat/long on the map.  Explore the data for each station, recording the station’s distance from the earthquake, the time at which the ground motion was detected at the station, and the maximum amplitude depicted in the seismograms. Student instructions and data sheet are provided.
   
   
10. Use these questions to guide follow up with the class:
    • Ask: Do you think people could feel the earthquake at all the locations you explored? Why or why not? 
    • How far is your school from this earthquake's epicenter? Do you think a station near here would have detected ground motion?
    • Explore this further by clicking on any station and then entering your zip code into the "Change station" box to access seismograms near your location. Ask: How close is this station to you, approximately?
    • Have students plot the latitude and longitude of the seismogram station closest to your school on the map (either the poster or individual maps or both).  If you are not sure if this station recorded the earthquake click on “See 24 hours of data at this station” then “ Show earthquakes (if any)” which will display a box around the area of the seismogram that represents the earthquake, if it was recorded there.
    • Ask: Did any one feel this ground motion? If no one felt the earthquake, have students offer ideas for why the seismogram shows the earthquake but humans did not feel it.
      
      
11. Optional: Access ShakeMaps from USGS to see the extent of noticeable ground motion from this earthquake.

ShakeMap sites provide near-real-time maps of ground motion and shaking intensity following significant earthquakes. These maps are used by federal, state, and local organizations, both public and private, for post-earthquake response and recovery, public and scientific information, as well as for preparedness exercises and disaster planning.

The maps provide a color coding of degree of intensity.  The values for Peak Velocity are in cm/sec and correspond to maximum amplitude observed in the seismograms (you’ll need to convert microns/sec to cm/sec).

Print the map or have students transfer the data to their world maps on which they have plotted the epicenter and station locations.  How does this representation compare to their predictions of whether humans could feel the earthquake at the different locations?

ShakeMaps are generated using instruments that estimate intensity of shaking.  The USGS also supports a program called “Did you feel it?” whereby residents can report their personal experience of the shaking and thus provides a ground truth to the instrumented data.  Data for this is sparser and has a time lag as people provide their reports in the days following the earthquake. This exploration is likely most fruitful for a large earthquake within range of well-populated continental locations.  (e.g. ocean-centered or island based earthquakes usually do not include data beyond the shores of a landmass.

Assessment

Student worksheets and maps could be collected as an assessment of data gathering and latitude/longitude plotting skills.

Extension

Follow news of the earthquake though a variety of on-line reporting services.

Earthquake Headlines

Be forewarned the sites linked to in these returns may contain advertising unrelated to science and education.  You may want to prescreen this site for appropriateness for your students.

Resources used

ShakeMaps
http://www.teachingboxes.org/catalog.jsp?id=TBOXR-000-000-000-164

Rapid Earthquake Viewer (REV)
http://rev.seis.sc.edu/

Did you feel it?
http://www.teachingboxes.org/catalog.jsp?id=DLESE-000-000-001-773

Earthquake Headlines
http://www.teachingboxes.org/catalog.jsp?id=TBOXR-000-000-000-154