Exploring North American Earthquakes
By Joseph J. Kerski
Only users who have a full version of ArcView can continue with this section.
Part 7: Earthquakes Respect No Boundaries
In this part, you will determine how many earthquakes occurred in each country through advanced GIS investigations.
The USGS says they need to focus research on the countries that contained the most earthquakes from 1973-1994. How will you find this information? To solve this problem, first examine the table associated with the earthquakes .
- Does this table indicate which country the earthquakes occurred in?
Therefore, you need to join the country information from the administrative boundaries file to the earthquakes data so that you can determine which earthquakes were inside each country.
First, save your project again.
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 .
Go to the File-->Extensions menu.
Add the “GeoProcessing” extension. This adds a choice to the “view” menu.
Access the geoprocessing extension by pulling down: View--> GeoProcessing Wizard. This is the new menu choice that you added by accessing the geoprocessing extension.
Go to: Assign Data by Location, and click Next.
Next: Assign data to earthquakes from administrative boundaries.
- Examine the earthquakes table . What new fields have been added?
Click on the field “admin_name”.
Go to Field --> Summarize. Give the resulting file and appropriate name (such as quakesbycountry.dbf) and location and click “OK”. Do not fill out anything else in the dialog box.
Examine your new table. Sort the table on “count”.
- What does the count in the FIRST row of the summary table represent?
- Which administrative area had the most earthquakes? Why?
- Does this match what you expected? Why or why not?
- How many were there in that administrative area?
- Go to the map and access the administrative boundaries theme. Find out where this state is, and indicate the pattern of earthquakes there.
Go back to your quakesbycountry table.
- What state in Mexico experienced the most earthquakes?
- Go to the map and access the administrative boundaries theme. Find out where this state is, and indicate the reasons for the frequency of earthquakes there.
- Which province or territory in Canada experienced the most earthquakes?
- Go to the map and access the administrative boundaries theme. Find out where this area is, and indicate the reasons for the frequency of earthquakes there.
- What administrative areas in the Caribbean Sea experienced the most earthquakes?
- Go to the map and access the administrative boundaries theme. Find out where this country is, and indicate the reasons for the frequency of earthquakes there.
- Were any states in the USA without earthquakes? Why? Include in your answer how you found out this information.
- Were any states in Mexico without earthquakes? Why?
- Were any provinces or territories in Canada without earthquakes? Why?
Save your project, close your project, and exit ArcView.
- Congratulations! You have completed the assignment and are ready to submit your results to the USGS. You 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.
- Indicate at least three things that you have learned about earthquakes in North America from this lesson to this point.
- Indicate at least three things that you have learned about GIS in this lesson to this point.
Give a presentation on earthquakes in North America to your class, school, or community group. Include in your presentation:
- Why earthquakes are a serious international natural hazard.
- Where earthquakes occur in North America
- The relationship of cities, volcanoes, fault lines, and other features to earthquake epicenters
- How GIS can aid in analyzing earthquakes and other spatial phenomena.
- What you think the national and international community should do about earthquake preparedness.
Loma Prieta, California, Earthquake October 17, 1989. Crack system near Summit Road, half a mile southwest of Highway 17. View is northwest. A wide zone of dominantly extensional cracks passes several feet in front of the house. Figure 10-A, U.S. Geological Survey Circular 1045. Circular-1045 (http://188.8.131.52/ci1045.htm), Digital File:pla00036, ID. Plafker, G. 36