Week 7: Investigating Global Earthquake Activity

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Intro to Mapping Tabular Data in ArcGIS

In the first few weeks of this module you have used GIS to explore many types of shapefiles. Whether looking at city populations, river drainage areas or invasive species counts per county, we have provided you this data. This week we will start to add point data from longitude and latitude documents. GIS can easily draw this data as a point feature once imported into a GIS from a table of data. With this technique in your skill "toolkit" you can easily add data from thousands of sources, or even create your own data with a GPS unit.

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Download Geographic Data About Earthquakes

  • Right-click on the PC to download the zipped file below.
    EarthquakeAM.zip (Zip Archive 14.6MB Mar28 10)
  • Unzip the file. A folder called EarthquakesAM will be created.
  • Move the entire EarthquakeAM folder to inside the folder of Week7. The navigation path should be: (Path: c:/eyesinthesky2/week7/EarthquakeAM)

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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 row being the earliest event and so on.

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

Examine the excerpt of a table of numbers and other information pictured below. This table shows earthquakes that occurred in 2009. The data table is similar to other attribute tables that you have been working with so far 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 environment.

The classic example of a map illuminating the answer to a complex problem was John Snow's pump handle 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 convert 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 and save these kinds of data into a native GIS format.

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Launch ArcGIS and Open the Earthquakes Project

  • Launch ArcGIS ArcMap by double-clicking its icon on your desktop or Launch Bar.
  • Choose File > Open, navigate to c:/eyesinthesky2/week7/EarthquakeAM, select the EarthquakeAM.mxd file, and click Open.
  • A global map opens with the Continents, US States, and Lines of Longitude and Latitude on the map.

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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.

Cartesian Coordinate System Map showing XY (longitude, latitude) coordinates.

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Put Tabular Data on the Map

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Add Earthquake data from 2009

To map the 2009 earthquake events using Longitude and Latitude coordinate, select Tools > Add XY Data. The Add XY Data window opens. Navigate to the file named 2009EQ.csv. (c:/eyesinthesky2/week7/EarthquakeAM/csv_files). Select Longitude for the X Field and Latitude for the Y Field. The options in the Add XY Data window are as follows:

  • Select X field: Longitude
  • Select Y field: Latitude
  • Click OK.
  • The 2009EQ.csv file will add to your Table of Contents. Accept the symbolization that is automatically selected by the program. The colors are randomly selected and may differ from your own symbol colors.

The 2009 Earthquakes will now be displayed on the map.

21 Map with XY EQ

Note: If you miss-assigned the X and Y fields, the data will look strange, perhaps in a straight line, or as a single dot or in the wrong part of the world. Just right click and delete the new layer then repeat the steps above. The most common problem is switching the Latitude and Longitude (i.e.Latitude as X and Longitude as your Y fields).

You can see with your mouse that the X coordinate changes moving from one longitude line to another on the map and the Y coordinate changes as you move between lines of latitude.

At the end of this lesson you will export a corresponding shapefile to the XY layer in the Table of Contents. After you create a shapefile of your XY data, the computer will ask if you want to add it to the project. Alternatively you can click the Add Data button and look for the shapefile of the same name as the original table in the Earthquakes CSV file folder

For the 2009 Earthquake data, you will find a file called 2009EQ.shp, that has a .shp extension.

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Classify and Symbolize the 2009 Earthquake Data

Once the earthquake data is on the map, it is possible to Classify and Symbolize it.

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Classify the 2009 Earthquakes by Magnitude

To open the Properties window for the 2009 earthquakes layer, right-click the 2009EQ Event layer in the Table of Contents. Choose Properties from the menu. Then select the following options:

  • Draw features using: Quantities > Graduated Symbols
  • Field Magnitude
  • Classes 5
  • Style Circle1
  • Classified by Equal Interval
  • Size Start 2 and End 12
  • Click OK

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Classify the 2009 Earthquakes by Depth

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

  • Draw features using: Quantities > Graduated Colors
  • Field Depth
  • Classes 4
  • Style Circle1
  • Classified by Manual using break points at 10, 70, and 300 km
  • Color Yellow to Blue color ramp
  • Click OK
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Convert XY Data to Shapefile

To get full functionality from your XY points, it is necessary to convert your XY point (event) layers to shapefiles. It is a simple two step process.
  • Right click on the 2009.csv Events layer. Click on Data > Export Data.
    1 Data Export Data
  • Navigate to project folder and clickOK.
    2 Export Data to Shapefile

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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.
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Choose Another Tabular Dataset to Add to Your Map

Navigate to the csv_files folder and select another file to add to your map.

These files were downloaded from various Internet sites. To learn more about the datasets, click on the show me below or on the .txt files included with the csv_files. 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 available to choose from in the folder:
  1. 2010 Earthquakes - (2010_quakes.csv)
  2. Groundwater monitoring sites - (GW Monitor Sites.csv)
  3. GW 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)

Double click on your selection. Repeat the steps above to bring the data into ArcGIS using Add XY Data.

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 is projected on the map, Classify and Symbolize the dataset that you have added to you map.

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Explore More If You Have Time

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


Movies on this Page

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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.

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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 XY Data in ArcGIS

Movie Icon [link http://serc.carleton.edu/details/files/21281.html Classifying Earthquakes by Magnitude' new ]

Movie Icon Classifying Earthquakes by Depth in ArcGIS

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iPod Versions

Download these version to play on your iPod or iPhone.

Movie Icon Adding XY Data in ArcGIS

Movie Icon Classifying Earthquakes by Magnitude in ArcGIS

Movie Icon Classifying Earthquakes by Depth in ArcGIS