Mapping Earthquakes in Northern California


Table of Contents

  1. Mapping Earthquakes in Northern California
  2. Setting Up Your Workspace
  3. Downloading Data from Natural Earth
  4. Download Data from the Northern California Earthquake Data Center (NCEDC)
  5. Skill Drill: Download Data from the United States Census Bureau
  6. Adding California as a Basemap Layer
  7. Skill Drill: Adding the Humboldt County Boundary as a Basemap Layer
  8. Adding XY Data
  9. Changing the Map Projection of the Data Frame
  10. Representing Earthquake Magnitude Using Graduated Symbols
  11. Changing the Map Size and Position
  12. Creating an Inset Map
  13. Inserting A Map Title
  14. Inserting a Map Legend
  15. Inserting a North Arrow, Scale Bar, and Acknowledgments
  16. Exporting your map as a PDF file

Download Data from the Northern California Earthquake Data Center (NCEDC)

UC Berkeley Seismological Laboratory created the Northern California Earthquake Data Center. Using the Chrome browser, navigate to the Northern California Earthquake Data Center (NCEDC) website at http://ncedc.org/ncedc/catalog-search.html. The catalog has quite a few search settings which at first may seem confusing. In this activity, we will not cover all of the details related to the settings. To find out more about how to use this website and to learn about the options available, you can click the help link to read the additional documentation. For the input catalog, choose USGS NCSN Catalog 1967 – Present. For the output format, pick NCSN catalog in CSV format.

An image of the NCEDC Input and Output Catalog settings
The image here shows the NCEDC Input and Output Catalog settings.

For the earthquake parameters center the values from the table below:

Start Time2017/01/01

 

End Time2017/12/31

 

Min Magnitude3.0
Min Latitude32
Min Longitude-114
Max Latitude47
Max Longitude-130
Event TypesEarthquakes
An image of the NCEDC Earthquake Parameters
The image here shows the NCEDC Earthquake Parameters.

Leave all other Earthquake Parameter settings not mentioned here as default. Under Output Mechanism, select Send output to an anonymous FTP file on the NCEDC.

An image of the NCEDC output mechanism
The image here shows the NCEDC output mechanism settings.

When you are ready, click Submit request. In the Chrome browser, the results will load in a new tab. Under “output can be downloaded from:” click the link next to URL.

An image of the NCEDC search results
Data products for this tutorial were accessed through the Northern California Earthquake Data Center (NCEDC), doi:10.7932/NCEDC. Click to view a larger sized image.

The next page will display the data in CSV format. You will need to save the results to your Original folder.

An image of the NCEDC search results CSV in browser
CSV stands for comma separated values . As you can see on the page, each of the values is separated by a comma. Click to view a larger sized image.

In the Chrome browser hit Ctrl S to save. Browse to your Original folder. For the filename, enter “earthquake2017.csv”. Next to Save as type, choose All files. When you are ready, click Save. In Microsoft Windows navigate to your original folder and open the earthquake 2017 CSV to view the results. By default, a CSV file should open in Microsoft Excel.

If for some reason, the CSV file does not open in Microsoft Excel, right-click and select Open with, then choose Microsoft Excel as the default program.

When opened in Microsoft Excel, the CSV file appears as a table. The commas in the data create columns, also called fields, in excel. A row, also called a record, represents each earthquake. In this instance, the top row is different from the remaining records. It is made up of column headers, sometimes called field names. When working with geospatial data, this format is critical. The first row of any geospatial data table must contain the field names. You will learn more about these types of tables in a later chapter.

An image of the Earthquake data in excel
GIS data table must be in a particular format. The top row must contain the field names. Click to view a larger sized image.

Go ahead and close the CSV file in Microsoft Excel. In a later step, you will use the CSV file in ArcMap, and it is important not to have it opened in two places at once.