Global GIS Lesson: Part 5

Exploring North American Earthquakes

By Joseph J. Kerski

Part 5: Earthquakes Everyday

In this part, you will examine earthquakes by country in North America, and compare recent earthquakes to your existing data.

Make the 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 using the clear selection tool .

Make political boundaries and political boundary labels visible by checking the small boxes to the left of the theme names.

  1. What country will you list in your report to the USGS that appears to suffer the most earthquakes?
  2. Name two reasons, based on your observations of the map, why more earthquakes occur in this country than any other.

Make US Counties visible. With this map theme, notice that each state's counties are one color.

  1. What state will you indicate to the USGS has the most earthquakes?
  2. Name two reasons why you believe more earthquakes occur in this state than any other.
  3. Did any US states experience no earthquakes? Give two reasons for your answer.
  4. Change the legend from magnitude that you have been analyzing to examine the depth (“km” field) of earthquakes. Do this by double-clicking on the theme name to pull up the legend editor. Change the field name to depth, as follows:

Use this new legend by clicking on Apply.

Your new map represents the depth under Earth’s surface at which the movement occurred, in kilometers underneath the surface.

  1. Describe the pattern of the depth of the earthquakes and their distribution across North America.
  2. Is there a relationship between magnitude and depth? Why or why not?
  3. What is the relationship between magnitude to the plate boundaries? Why? You may need a reference for plate boundaries on a map, in a textbook, or on the Internet.
  4. What is the relationship between depth and the plate boundaries? Why?
  5. Are certain types of plate boundaries associated with certain earthquake magnitudes and depth? Summarize what you know and can find out about this topic.

Minimize your GIS session.

Access the USGS National Earthquake Information Center by using an Internet browser. This is the site in Golden, Colorado, that collects seismic information from all over the world.

  1. Select "Current Worldwide Earthquake List."
  2. XXXExamine this list. How many days does this information cover?
  3. Does the number of earthquakes surprise you? Why or why not?
  4. Are you familiar with any of these earthquakes? Did you hear about any of them on the radio, the newspaper, or on the Internet?
  5. How many earthquakes appear in the list?
  6. How many earthquakes occur each day? Show your work.
  7. Examine the information about the list on the NEIC web site. Does the list indicate ALL recorded earthquakes, or just the major ones? What is the cutoff criterion?
  8. What percentage of earthquakes in the list occurred in North America? Show how you determined your answer.
  9. Does the pattern of new earthquakes in North America fit the pattern you have been analyzing using your GIS tools and methods? Why or why not?
  10. Indicate at least three things that you have learned about earthquakes in North America from this lesson to this point.
  11. Indicate at least three things that you have learned about GIS in this lesson to this point.