Global GIS Lesson:

Exploring North American Earthquakes

By Joseph J. Kerski

Part 3: Investigating the Loma Prieta Earthquake

In this part, you will investigate one of the worst earthquakes ever to strike the United States, assess critical infrastructure, and assess the relationship of fault lines to earthquakes.

The USGS has indicated that your report needs to include an analysis of the following earthquake: In October 1989, as over 62,000 fans filled Candlestick Park for the third game of the World Series baseball game and millions of San Francisco Bay Area workers were commuting home, a major earthquake struck. This was the Loma Prieta Earthquake, damaging many neighborhoods in San Francisco and Oakland, and collapsing a major portion of an interstate highway in Oakland, killing many of the drivers.

Make themes you have been working with the active theme by clicking once on it. Use shift-click to select multiple themes. Clear any previous selections .

Open the earthquake table .

Query the table to find the Loma Prieta earthquake by its date and magnitude, as follows. Be sure to enter the information by clicking on the field names and equals sign.

Zoom to the Loma Prieta epicenter at a scale of 1:1,000,000. The scale is in the upper right of the map. You can type in the exact scale as 1000000 if you wish in the scale box.

1. In what part of California did this earthquake occur?
2. Use the identify button with the US Counties theme active to answer the following: In what county did the earthquake occur?
3. What direction from San Francisco was this earthquake’s epicenter?
4. Use the measure tool , answer the following. How far was the epicenter from San Francisco?
5. Based on what you just measured, discuss how an earthquake occurring many miles from San Francisco and Oakland could have caused damage in those cities.
6. Earlier, you considered the disruption that earthquakes pose to critical infrastructure. Turn on the airfields theme and name the nearest airfield to the earthquake.
7. Use the measure tool to measure the distance to this airfield.
8. Find the airfield at latitude 37.36 north and 121.93 west, the nearest international airport to the epicenter. What city is the airport associated with?
9. Have you ever flown into this airport? Ask to find out if any of your classmates have flown into this airport.
10. Make roads, railroads, and utility lines visible. Make at least four observations about the proximity of these features to the earthquake.
11. Have other earthquakes occurred in this area of California, or was the Loma Prieta earthquake an isolated case?
12. Turn on the US Faults theme and discuss the relationship between earthquakes in this part of California and fault lines.
13. Based on your investigations, indicate in your report to the USGS what you consider to be the two main reasons why this earthquake in October 1989 caused more damage and death than others in this area.
14. Do some research on the Loma Prieta earthquake and indicate your findings below.
15. How does your research enhance what you learned about Loma Prieta through GIS?

Next, you will examine faults in relationship to earthquakes throughout North America.

Turn off all themes except faults, Alaska faults, US faults, earthquakes, and the shaded relief base.

Zoom out to all of North America using the globe symbol on the Global GIS Tools menu.

It is difficult to detect the relationship of earthquakes and faults, because of the large number of earthquakes. Reduce this number by clicking on “earthquake tools” in your Global GIS window. Show magnitudes between 6 and 9, as follows:

16. Describe the relationship between fault lines and earthquakes. Consider these questions in your narrative: Do earthquakes usually, or always occur near fault lines? Do earthquakes ever occur away from fault lines? If so, where? Do you think this map shows ALL of the faults in North America, or just a few? How does this affect your answer?
17. Turn on earthquakes between 4 and 9, instead of 6 and 9. Does this affect your answer, above? Why or why not?
18. Turn on cities. Discuss the relationship between cities and fault lines for your report to the USGS.
19. Congratulations! You have completed the third part of the assignment and have contributed much to the understanding of earthquakes in North America. Indicate what you consider to be the most surprising thing you have learned in this part, the most interesting thing, and the most significant thing.

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