Student Instructions

Introduction to the Research Problem

Why should humans care about earthquakes?

Scientific understanding of earthquakes is of vital importance to the world. As the population increases, expanding urban development and construction works encroach upon areas susceptible to earthquakes. With a greater understanding of the causes and effects of earthquakes, we may be able to reduce loss of life and damage of property from this destructive phenomenon.

By exploring this module, you will learn:

• (1) How to define, identify, and describe natural disasters and distinguish them from natural hazards.
• (2) How to identify the extent of the problem of earthquakes and the reasons they occur.
• (3) How the pattern of earthquakes and its relationship compares to the pattern of human settlement.
• (4) How earthquakes affect the physical environment.
• (5) How humans have attempted to control the effects of earthquakes and other natural hazards.
• (6) That the choice to live in hazardous areas is complex, involving personal perceptions, risk, and freedom, and varies widely among people and places.

 
and be able to:
• (7) Download data from the Internet, map it, and analyze it.
• (8) Build your skills in the of a Geographic Information System (GIS).
The USGS is the USA's largest science agency. One of its missions is to study earthquakes, so that lives will be saved and destruction minimized. The USGS, through its National Earthquake Information Center records hundreds of earthquakes each month. The largest (usually above 3.0 in magnitude) are posted as soon as they occur on the Internet. You can download these earthquake data, map them, and analyze them.

Access and Manipulate Earthquake Data from the Internet

Go to the following site to find the earthquakes for the last few days. Keep the connection to that WWW site active, and then come back to this page for the next step. The site is at: http://wwwneic.cr.usgs.gov/neis/bulletin/bulletin.html.

Read the description of the data on this site.

Question: How many hours difference exist between your time zone and the Greenwich Mean Time listed on the Internet site?

How many hours and minutes have elapsed between now (the time you are working on this project) and the last earthquake?

How much time elapses between the time of an earthquake and the time it is posted on this Internet site?
 
 
 

Highlight the earthquake data with your mouse, making certain to include the column headings.

Copy this section that you highlighted (on a PC, use Control-C to copy). Open either a word processor or an ASCII text editor, and paste the text (on a PC, use Control-V to paste). Save your file in your own folder. Make sure you save the file as plain (ascii) text.

You can map these data in a Geographic Information System (GIS). A GIS is a computerized system for inputing, manipulating, analyzing, and plotting geographic data. The GIS will correctly map your data based on the longitude and latitude, which will act as the x and y coordinates, respectively. The name of the GIS that you will be using is called ArcView. ArcView GIS requires commas to exist between the data fields. It also expects west longitude and south latitude to be negative numbers, with no directional designations (N, S, E, or W). You must therefore edit your earthquake data before bringing it to the GIS.

Save your file as equake.txt in the same file equake.zip is in.  Save after each step in case you accidentally delete or change a piece of data inadvertently. Make sure you save the file as plain (ascii) text. Why? Again, because the GIS expects the data to be in text format.

First, begin by unzipping the equake.zip file.  To do this double click on the file and follow the winzip program instructions.  You do not need to add this file to the favorites file in winzip.  When it asks you where you would like to put the new unzipped files, put them in the same file the original equake.zip is in.

If you are using a PC follow the instructions labeled For Windows users.   If not, follow the instructions labeled For Non-Windows users further below.

For Windows users
 

•     You are now ready to make changes to the data that will allow ArcView to read and manipulate it.  To change the data to a format that ArcView recognizes, open a DOS window, change to the directory where your files are by entering CD \directoryname, and type finger.
•     A DOS screen will appear that says:  Name of input file in finger "format" [A80;CR= eqs.txt]?
•     Type the name of the file you would like to convert, in this case it should be eqs.txt then hit the enter key.
•     Now the screen should read:  Name of comma-deliminated file to be created [A80;CR= eqsgis.txt]?
•     Type a new name for the file that will be converted and ready to be manipulated in ArcView.  For example:  eqsgis.txt  then hit the enter key.
•     Now the DOS screen reads:  Stop - Program terminated.  This means that the program has converted your eqs.txt file to eqsgis.txt which can be read and manipulated by ArcView.



•     You can close the DOS screen and go to the instructions:
  Import Your Earthquake Data Into a GIS.


For Non-Windows users


Make the following changes: The changes affecting a small portion of the file will probably be easiest by moving the cursor and performing an edit. Changes affecting most of the file might be easiest using a global search and replace. Be careful and save often! The file has to be accurately edited so that the GIS will be able to read it.
 
 

• 1. Delete the second line below:

DATE-(UTC)-TIME    LAT    LON     DEP   MAG  Q  COMMENTS





yy/mm/dd hh:mm:ss   deg.   deg.     km

---

• 2. Delete any blank lines at the top of the document, making

certain that the following text is on the first line:

 DATE-(UTC)-TIME    LAT    LON     DEP   MAG  Q  COMMENTS

---

• 3. Place commas between each field in the title line: Change:

DATE-(UTC)-TIME    LAT    LON     DEP   MAG  Q  COMMENTS

To the following:

DATE,-(UTC)-TIME,    LAT,    LON,     DEP,   MAG,  Q,  COMMENTS

---

• 4. Place commas between each field in each line in the data itself: Change:

97/05/30  22:18:05   16.08N  97.89W  33.0   4.8Mb  B   OAXACA, MEXICO

To the following:

97/05/30, 22:18:05,  16.08N,  97.89W,  33.0, 4.8Mb, B,  OAXACA, MEXICO

---

• 5. Remove all commas in the comments field. Otherwise, the GIS will split up the comments where commas exist. For example, change:

97/05/30, 22:18:05,  16.08N,  97.89W,  33.0, 4.8Mb, B,  OAXACA, MEXICO

To the following:

97/05/30, 22:18:05,  16.08N,  97.89W,  33.0, 4.8Mb, B,  OAXACA MEXICO

---

• 6. The third and fourth fields are latitude and longitude, respectively. Place negative (-) signs in front of latitudes in the southern hemisphere, and longitudes in the western hemisphere. For example, change:

97/05/29, 10:21:05,  37.12N 121.50W  10.0 3.5ml A  CENTRAL CALIFORNIA 


97/05/29, 17:02:39,  35.91S 102.37W  10.0 6.1ms A  SOUTHERN PACIFIC OCEAN

To the following:

97/05/29, 10:21:05,  37.12, -121.50,  10.0, 3.5ml, A,  CENTRAL CALIFORNIA 


97/05/29, 17:02:39, -35.91, -102.37,  10.0, 6.1ms, A,  SOUTHERN PACIFIC OCEAN

---

• 7. Later, you will be able to classify earthquakes according to their magnitude, the sixth field. Six different magnitude types (MAG) may be quoted: Ml (local, the original Richter magnitude), Lg (mblg), Md (duration), Mb (body wave), Ms (surface wave), and Mw (moment). To enable the GIS to map according to magnitude, you must take out these magnitude text strings, thereby making the field numeric. For example, change:

97/05/29, 10:21:05,  37.12, -121.50,  10.0, 3.5ml, A,  CENTRAL CALIFORNIA 


97/05/29, 17:02:39, -35.91, -102.37,  10.0, 6.1ms, A,  SOUTHERN PACIFIC OCEAN

To the following:

97/05/29, 10:21:05,  37.12, -121.50,  10.0, 3.5, A,  CENTRAL CALIFORNIA 


97/05/29, 17:02:39, -35.91, -102.37,  10.0, 6.1, A,  SOUTHERN PACIFIC OCEAN

---

• 8. Verify that you have made changes listed in steps 1 through 7 above. After making these changes to the earthquake epicenter file, it should look like this:

 

 
 
 
 
 
 
 
 
 

You can look at point, line, area, and image data. Points represent data such as traffic lights or trees. Lines represent data such as pipelines or roads. Areas represent data such as states or lakes. Images are aerial photographs, computer-generated images, or satellite images.

You have manipulated your data -- it is now ready to bring into ArcView GIS.

Open ArcView GIS.
Select File --> New Project.


Click Views, and New.
Select Theme --> Add Theme.
Under the folder you have saved the unzipped equake.zip files:
Add world30.shp
Add cntry94.shp
 
 

Click on the small boxes associated with each theme to make them appear.
 
 

File-->Save Project. Save your project in your own directory.

Add your earthquake data. Click once on Tables. Click Add.

Recall that you changed your data to comma delimited text. In the lower left part of the window, change the field to delimited text (*.txt) to indicate that this is the type of file you will add.

Find your text file in your folder and click OK.

You have just converted your raw text file into an ArcView-readable table. Your table name should now appear in the list of tables along with a window with the data inside.

Click on the View window to make it active.

Go to the View menu and select Add Event Theme.

Your text file should appear. If not, type in the directory and name of your text file.

Click OK.

Note that the x coordinate represents longitude, and the y coordinate represents latitude.

Make the theme appear by clicking on the small check box next to it.

File-->Save Project. Name the project and save it in your own folder. Your data should look like this:
 
 

Now you are ready to analyze the data you have mapped and draw some conclusions about it.

Examine the pattern of earthquakes.

Describe the pattern of earthquakes.

Add the theme "plat_lin.shp." These are the boundaries of the crustal plates.

What is the pattern of earthquakes related to plate boundaries? Did more earthquakes occur this week near plate boundaries or far away from the boundaries?

Add the theme cities.

View-->Add Theme.

Zoom in on the world map and analyze the location of earthquakes and look at major cities. Single click on cities.shp in the legend, but do not click on the check mark box. Drag it below the earthquake theme.

What is the pattern of earthquakes related to cities? Are most cities near earthquake epicenters?

Why do people live in hazardous zones? What influences the choices that make people migrate or choose not to migrate? What are the everyday risks that you face in going to school, going to work, traveling, and so on? How do you decide which risks are worth taking?

Double click on the theme earthquake.txt to bring up the legend editor.

Change the legend type from "single symbol" to "unique value."

Change the values field from "none" to "date."

Your data should look similar to this image. Note that this image is zoomed in to part of North and Central America.

Look at the count to the right of each category. Does the same or similar number of earthquakes occur each day of these magnitudes? Which day saw the most earthquakes, and what was the frequency? Which day saw the least earthquakes, and what was the frequency?

File-->Save Project.

Now you are ready to create a final plot of your data for your presentation. Your final plot will be contained in a layout.

Layout--> New

Click on the Frame button (the last one on the right on the button bar).

Drag this to the first choice--the icon that looks like a globe. Let go of the mouse to select this and add a View Frame.

Draw a rectangular frame on the layout.

Click on View1 to insert the view in the frame.

Go to the second choice under the frame button, which looks like a legend. Draw a rectangular frame to create your legend.

Go to the fourth choice under the frame button to add your north arrow. Draw a rectangular frame to create your north arrow.

Click on the "T" button to add text on the button bar.

Click in the layout.

Type in text. You could include facts about earthquakes, your name, the date, a title, or other information that your audience would find useful. Be creative, remembering that your final map will represent part of what you learned in this module.

Plot your layout.

File-->Print.

Repeat the above exercise one week later. Append the new data to the old. Note the differences in the frequency and intensity of the new earthquakes. Why have they changed?

Plot the new data and note the pattern. Is the pattern of the new earthquakes over the earth's surface similar to or different from that of the previous week? Why or why not?

Repeat the above exercise for an entire year's worth of earthquake data, available at the ESRI Educational GIS site.

What patterns are different comparing 1 week of earthquakes to 1 year of earthquakes? What patterns are the same? How many earthquakes occurred during the year you are analyzing?

On to the Supporting Materials -OR- Return to the Table of Contents