Global GIS Lesson: Part 2

Exploring North American Earthquakes

By Joseph J. Kerski

Part 2: Digging Deeper

In this part, you will examine the relationship between earthquakes and cities, and investigate earthquakes in a specific area in California.

Click on the Advanced Interface button at the bottom of the Global GIS Tools window. You will notice the additional tools now at the top of your computer screen.

Make major cities the active theme by clicking once on it. Clear any previous city selections Clear selection tool.

Make earthquakes the active theme by clicking once on it. Clear any previous earthquake selections Clear selection tool.

Under the Theme pull-down menu, press "Select By Theme" to discover how many earthquakes are within 50 kilometers of major cities.

 Select by theme

Examine the resulting earthquake table Open Theme Table icon. Look in the upper left of your computer screen.

  1. How many earthquakes resulted from your query of the data?
  2. What percentage of North American earthquakes are within 50 kilometers of major cities? Show how you determined this answer.
  3. Make 3 observations about the pattern of earthquakes near California cities.
  4. Compare the amount of earthquakes in Alaska versus California. Which state would you say receives the most earthquakes?
  5. Which state would you say receives the most publicity about earthquakes in newspapers, television, radio, and on the Internet?
  6. Compare your answers to the two previous questions. Did you write a different answer for the two questions? If so, why do you suppose this is the case?

As you move around the map, notice the latitude and longitude values to the upper right of the view (map) window.

Zoom to the earthquakes at 36.91 north latitude and 121.65 west longitude. Set the scale to 1:10,000. There will be two earthquakes at this exact spot.

  1. Identify Identify icon these earthquakes and indicate their magnitudes:

Click on "Global GIS Help" GIS help in Global GIS Tools. Go to "Datasets" and select the earthquakes theme.

  1. What field name contains the time when the earthquakes occurred?

Based on this information, go back to your map and examine the time when the three earthquakes occurred. List the earthquakes below in the order of their occurrence.

  1. Were these earthquakes associated with the same seismic event? Explain your answer.
  2. What is an aftershock?
  3. Do you think the earthquakes you are examining include an aftershock? If so, which earthquake was an aftershock of the first?
  4. Notice the “feature search radius settings” near the bottom of the Global GIS Tools window.

 Search radius 50km

Drag a new search radius – a circle -- from these two earthquakes until the circle just touches the Pacific coastline. This should be a 13 kilometer search radius, and the number 13 should appear in the kilometers field.

Generate a map report Generate report and click on the earthquake on the map again. Print the map report of this area.

  1. Summarize what this report tells you in your own words.

You need to assess possible damage from future earthquakes in this region in your report, in terms of roads, airports, and population.

  1. What is the 1998 population within 13km of these earthquakes?
  2. Who, in your opinion, are the most vulnerable segments of the population to earthquakes?
  3. How far is the nearest road from the earthquakes?
  4. Do you think roads could be damaged by earthquakes? Name three ways roads could be damaged.
  5. How could the disruption of transportation affect evacuation from an earthquake and rescue operations?
  6. What is the name of the nearest airfield to these earthquakes? How far is it from the earthquakes?
  7. Do you think an airfield could be damaged by an earthquake? Describe three ways air services could be disrupted.
  8. Congratulations! You have completed the second part of your mission 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.