Week 7: Investigating Global Earthquake Activity

top of page

Intro to Mapping Tabular Data in AEJEE

In the first few weeks of Module 2, you used GIS to explore many types of databases and their associated shapefiles. Features that can be drawn as points can be imported into a GIS from a data table. Once you have this technique in your skill toolkit, you can easily add data from thousands of sources, or even collect your own data with a GPS unit to add as a map layer.

top of page

Download Geographic Data About Earthquakes

  • Right-click (Win) or control-click (Mac) the link below to download the zipped file.
    EarthquakeAE.zip (Zip Archive 14.5MB Mar26 10)
  • Unzip the file. A folder called EarthquakesAE will be created.
  • Move the entire EarthquakeAE folder into the Data folder inside the AEJEE folder. (Path: ESRI/AEJEE/Data/EarthquakeAE.)

top of page

Explore a Table of Data

Think about the last time you collected a set of data. You probably set up a data table with headers indicating the data you wanted to collect, including the units that would be collected. The rows of that table were set up to hold the data for each individual record or event that you planned to collect. As you made observations, you filled in the data table with whatever observations you made of each event. The table was probably organized sequentially, with the first rows being the earliest events and so on.

After the experiment was concluded you used this data table to analyze your results. Maybe you graphed the data or looked for patterns or clusters in the data. You may have used a spreadsheet program to analyze this data, especially if you were doing a more complex analysis.

Examine the data table below. It contains both numerical and descriptive data. This table shows earthquakes that occurred around the world in 2009. The data table is similar to other attribute tables that you have worked with in this course.

Thought Question: What are the advantages and disadvantages of working with data in a tabular format?

What is absent in exclusively tabular data is the opportunity to easily inquire about spatial relationships. Fortunately, many Earth and environmental science datasets available today include some sort of geospatial reference. When the spatial data, or Longitude/Latitude data, (also called X, Y data), are included alongside other information, it is possible to place that data onto a map and see it in a richer, more complete context.

The classic example of a map illuminating the answer to a complex problem was John Snow's water pump and cholera incidence map. Can you think of other patterns that are more easily understood with a map than a list or table of data?

GIS software can bring any table or delimited list of information into a GIS map if coordinate data (Longitude and Latitude) are included with it. This week you will learn how to import these kinds of data.

top of page

Launch AEJEE and Open the Earthquakes Project

  • Launch AEJEE by double-clicking its icon on your desktop or by clicking its icon in the Dock (Mac) or Launch Bar (Win).
  • Choose File > Open, navigate to ESRI/AEJEE/Data/EarthquakeAE, choose the E_QuakesAE.axl file, and click Open.
  • A base map opens, showing Continents, US States,and Lines of Longitude and Latitude.

top of page

Review How Longitude and Latitude Appear on the Map

Move the cursor across the map to remind yourself how the X and Y coordinates relate to Longitude and Latitude. Start at the far left side of the map and move your cursor horizontally to the right all the way across the map. The X and Y coordinates are shown in the lower left corner of the map. Notice how the X coordinates show changes in longitude. Move your cursor vertically from the bottom to the top of the map. Notice how the Y coordinates show changes in latitude.

reading_lat_lon_annotated_aejee Map showing XY (longitude, latitude) coordinates.

top of page

Put Tabular Data on the Map

top of page

Add earthquake data from 2009

To map the 2009 earthquake events using Longitude and Latitude coordinates, choose View > Add Event Theme. The Add Event Theme window opens. Click the Browse browse button button to navigate to the file named 2009EQ.csv. (Path: ESRI/AEJEE/Data/EarthquakesAE/csv_files). Choose Longitude for the X Field and Latitude for the Y Field. Draw the events using symbols that are Blue Circles with a point size of 5. The options in the Add Event Theme window are as follows:

  • Table: ESRI/AEJEE/Data/EarthquakesAE/csv_files/2009EQ.csv
  • X field: Longitude
  • Y field: Latitude
  • Draw event using symbol with:
    • Style: Circle
    • Color: Blue
    • Size: 5
  • The Output Directory defaults to the current csv_files folder that you opened the earthquake file from. Accept this default.
  • Click OK.

The 2009 Earthquakes will now be displayed on the map. (Be patient. Adding an event theme especially one with many features may take time, especially on slower computers.)

Note: If you enter the X and Y fields incorrectly, the data will either not project or will project incorrectly. Repeat the steps above.

The most common problem is choosing the wrong fields to use for Latitude and Longitude. Recall that X coordinates represent the vertical, or longitude, lines on the map and Y coordinates represent the horizontal, or latitude, lines.

The good news is you only have to go through this import process once. When AEJEE imports and projects a tabular dataset onto a map it automatically creates and saves a corresponding shapefile. The next time you want to see this dataset on your map as a layer, just click the Add Data button and look for the shapefile of the same name as the original table in the Earthquakes csv files folder. For the 2009 Earthquake data, you will find a file called 2009EQ.shp, that has a .shp extension.

Movie Icon

top of page

Classify and Symbolize the 2009 Earthquake Data

Once the earthquakes are displayed on the map, you can Classify and Symbolize them.

top of page

Classify the 2009 earthquakes by magnitude

To open the Properties window for the 2009 earthquakes layer, right-click (Win) or control-click (Mac) the 2009EQ label in the Table of Contents. Choose Properties from the menu. Then select the following options:

  • Draw features using: Graduated Symbols
  • Field Magnitude
  • Classes 5
  • Style Circle
  • Classified by Equal Interval
  • Color Start White and End Red
  • Size Start 2 and End 12
  • Click Apply and Click OK

Movie Icon
top of page

Classify the 2009 earthquakes by depth

To open the Properties window for the 2009 earthquakes layer, right-click (Win) or control-click (Mac) the 2009EQ label in the Table of Contents. Choose Properties from the menu. Then select the following options:

  • Draw features using: Graduated Symbols
  • Field Depth
  • Classes 4
  • Style Circle
  • Classified by Manual using break points at 10, 70, and 300 km
  • Color Blue and End Red
  • Size Start 2 and End 2
  • Click Apply and Click OK
Movie Icon

top of page

Explore other classification and symbolization options

Try symbolizing the data by Month, or change from Manual classification to Equal Interval to Quantiles. When you are done, close the Properties window.
top of page

Choose Another Tabular Dataset to Add to Your Map

Navigate to the csv_files folder and select another file to add to your map as an event theme.

These files were downloaded from various Internet sites. To learn more about the datasets, click on the show me below or open and read the .txt files in the csv_files folder. These datasets represent a range of interests and are not intended to all magically fit together into one coherent story.

Below is a list of the data files you can choose from in the folder:
  1. 2010 Earthquakes - (2010_quakes.csv)
  2. Groundwater monitoring sites - (GW Monitor Sites.csv)
  3. Groundwater temperature - (GW_temperature.csv)
  4. Journey North Hummingbird Migration Patterns - (Journey North HB 20093.csv)
  5. Significant and Big Historical Earthquakes - (sig_big.csv)
  6. Tornado Touchdowns in the United States 1950-2008 - (tornado touchdowns.csv)
  7. US Thermal Springs - (US Thermal Springs.csv)
  8. World Glaciers - (World Glaciers.csv)

Repeat the procedures you learned above to bring the data into AEJEE using Add Event Theme.

Look for the Latitude and Longitude headers in the data table to assign coordinates to the attributes.

Note: The Latitude and Longitude Fields may be named slightly differently in each case. Also, some of these files are large and may take a few moments to draw on your map. Be patient.
For example:
  • Latitude may be also be labeled - LAT, Lat83, or lat.
  • Longitude may be also be labeled - LONG, or Long83 or long.
Learning to decode the headers in an attribute table is an important skill in becoming independent in the use of data and while there are some conventions for naming data, there remain a large variety of nuances.

If at first you don't succeed, try again!

Once the data are displayed on the map, Classify and Symbolize them in an appropriate way.

top of page

Explore More If You Have Time

  • Add other data layers from this project folder or other datasets included in the AEJEE download.
  • Explore possible relationships between datasets.

top of page

Movies on this Page

top of page

How to download movies

  • Click the link to go to the SERC media library listing for the movie. The record will open in a new window.
  • On the SERC media library page, right-click (Win) or control-click (Mac) the link (below the movie on the Flash version pages) to download the movie file to your hard drive.

top of page

Flash Video Versions

Download these versions to play on your computer. You'll need an appropriate movie player to view the file, such as Flash Player, Real Player (Mac / Win), or Adobe Media Player.

Movie Icon Adding an event theme in AEJEE

Movie Icon Classifying Earthquakes by Magnitude in AEJEE

Movie Icon Classifying Earthquakes by Depth in AEJEE

top of page

iPod Versions

Download these version to play on your iPod or iPhone.

Movie Icon Adding an event theme in AEJEE

Movie Icon Classifying Earthquakes by Magnitude in AEJEE

Movie Icon Classifying Earthquakes by Depth in AEJEE