exercise 2 mapping seismic...

Geol 3050 – GIS for Geologists – Exercise 2

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Exercise 2 Mapping Seismic Activity Due: Thursday, January 23 by the start of class!Goal: Get familiar with ESRI ArcMap. Explore all functions on the Tools-toolbar. Do some simple geologic analyses in ArcMap. Note: Make sure you answer parts A, B, C, D, E and F ______________________________________

1. Where are earthquakes located?A. Download and unzip your data as described in Exercise 1:• Make a new work folder for today on the D-drive (if it’s not already there):• Or put the data on your flash drive (recommended)• Download your Exercise2.zip data from:

http://geode.colorado.edu/~geol3050/Data/ • Unzip your data, if needed

B. Building a base map.• Start ArcMap by going to

START menu > Programs > ArcGIS >ArcMap• ArcMap will now open (choose from New Maps in the left window, and My Templates will pop up

in the right window; then choose Blank Map).• You will now see this:

Look around carefully – Let your mouse go over every icon you see and read the short description that lights up. Also try every menu item and see what is there.

Table of Contents Data View Tools‐ toolbar


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You can “dock” the Tools-Toolbar anywhere you want…

• Find and use the add data button to add the files we will need today

and browse to the folder where you stored your exercise data for today.

• Before you will be able to do that you need to make a connection to the dataset-location, by usingthe following button and browsing to the right location:

In your case the location will be D:\Users\yourname\GIS\Exercise2 or your FlashDrive path

• Browse to the correct location and add the file “country.shp”

Note that a map appeared in the “Data View” window, and that the country.shp file is now displayed in the “Table of Contents” as the “Layer” file ‘country’.


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• Toggle the √ check box next to the word country … and note what happens.

• Change the color of the countries:Doubleclick the little rectangle below the word country. The following window will open:

• Change the fill color to Yucca Yellow (circled on the color chart above)We will keep the color of all the countries the same for now to focus on the seismic data.

• Add the layer quakes2000.shp (use the same technique as for countries.shp):Only today, ignore the Geographic Coordinate Systems Warning box by clicking close.


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Your map should look like this. Note that the earthquakes are represented by points and that the countries are mapped by polygons! Also, note that the points are automatically placed on top of the polygons, so you can see them.

• Change the order of your Table of Contents (below the word Layers) and move the quakes underthe countries. First, click on the leftmost tab in the layers display. Then left-click on the“quakes2000” and hold-drag to move below the countries… Then move back to see all quakes.

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It is always a good practice to SAVE your work. Go to File > Save or Ctrl+S (as in most other programs) to do this. Save your file in the D:\Users\yourname\GIS folder you made and call it Excercise2.mxd. If you like, check out how this looks in ArcCatalog (use the Preview button). _______________________________________________________________________________

Observe the following: • Your map document is a gathering of the quakes and countries layers (shapefiles in this case). The

map document itself is just a compilation of the files to make our map.• That means that if we lose the map document (*.mxd) or forget to save, the data layers will still be

there. We would just have to re-add them to our map and re-classify them!_______________________________________________________________________________

2. How can I map the magnitude of the earthquakes?One of the most powerful tools you have for mapping your data is the ability to use different colors and sizes of icons to represent the data. For today, we will classify the data without going into all the other options we have…

• Go to the quakes layer (Table of Contents) and Right-once click on the word quakes2000

• Once in the Layer Properties window, select the Symbology tab.o If you get a warning about the maximum sampling size here or below, ignore it for today.


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• Pick out “Quantities”o Graduated colorso Value field: “Mag” (for magnitude”)o And pick a color ramp from green to redo Leave the rest at default (for today!)

• You will now see the following map, with the higher magnitude quakes in red and the lowermagnitude quakes in green:

• Get a feel for the map and look at the high and low magnitude values. What does the pattern tellyou?


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• Add the layer “plate_ln.shp” to your map document (as done before with the countries andquakes2000). This is a layer file containing the tectonic plate boundaries in the form of LINES.

• Again, just for today, ignore the warning about the unknown spatial reference.

• We now have points, polygons and lines in our map.

• Because lines are placed below points when added to a map, the plate_ln layer needs to be movedon top of the quakes2000 layer to be able to see anything! Click-drag the plate_ln layer above thequakes2000 layer. (As done in Chapter 1 today).

• Change the line color if you like (this works the same as changing the color for the countries).Either once left click on the line under plate_ln in the Table of Contents or Properties > LayerProperties > Symbology > Single Symbol.

• Use Pan, Zoom-In, Zoom-out from the Tools- toolbar and take a few minutes to explore your map.

In case you get lost: use the Zoom-to-full-extent button (the globe).

You must have noticed that the green colors (representing lower-magnitude quakes) tend to be clustered around the western part of the United States and in Europe. GIS is very powerful in noticing patterns like this. As a next step, we’ll use investigate the locations of these “smaller” quakes and start to have a look at Colorado.

• Add the layer ColoradoCounties.shp

• Notice that you probably cannot see it very well.o Right-click on the newly added layer and select “Zoom to Layer”.


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This will re-center and zoom your map to Colorado.

• Or, you can also use the zoom-in and panning (hand-)tools if that feels more natural to you.• How many earthquakes occurred in Colorado in the year 2000?• Use the Identify tool on your toolbar and click on each earthquake dot. Make sure you select the

“quakes2000” layer in the “Identify From” drop-down list.

• What were the depth and magnitude (Mag) of each quake?• Were there any earthquakes reported in Boulder County?

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Note! this is part A of what you need to hand in… • Create a Word document, with your name on it and Exercise 2 on the top.• Open Microsoft Word via the start Menu (as you did for ArcMap today).• If you can, make a table looking like the one below.• If you are not so familiar with Word, you can also just use spaces and TABs to align your

data in columns. Make enough rows for the earth earthquakes• Write down for each earthquake in Colorado (only) the magnitude and depth:

EARTHQUAKE DEPTH MAGNITUDE 1 5 3 2 3 Etc..


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• Now, find Japan with the “Find” tool. This tool looks like binoculars in your Tools box.

• Right-click on the result and select “Select”

• Go to the Selection menu at the top of your screen and choose “Select By Location” to select allthe earthquakes within 100 km of Japan’s borders:

• You will notice that now the country and all the earthquakes within 100 km of it are all selected (inlight blue).


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• Go to the quakes2000-layer in the Table of contents.o Right-click on the layer and select Open Attribute Table:

• Behind each GIS file (layer), there is a table:

• Click on the “Selected” Button at the base of the Table.• Note how you only see the selected records (everything is highlighted in blue).• Go to the Mag field, right click and select “Statistics”.


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• You will now see a window that looks like this (the values in yours will look slightly different):

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Note! this is part B of what you need to hand in… • Add the statistics information for the quake magnitudes and depths (just change the field in the

Statistics Dialog) in Japan in a table (or nicely organized columnar text) to your Word document:

• Note how many records are selected!_______________________________________________________________________________

• Deselect all layers in your map via the Selection Menu > Clear Selected features; or use the buttonin the Tools toolbox.

OR

JAPAN MIN MEAN MAX Magnitude Depth


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! This is part C of what you need to hand in…

o Go to the Table and repeat the statistics procedure and fill out the following table (there are no bluerecords anymore!):

Answer these questions: • How do Colorado and Japan fit in the global statistics (compare the minimum, mean, and

maximum values)?• How many earthquakes occurred each in Japan, Colorado and the world (list the total number of

earthquakes for each)o HINT: look at the number of total records in the table for the world, the number of selected

records for Japan and the total number for Colorado…o How many peaks are there on the worldwide frequency distribution of earthquake

magnitude? (i.e., how many “humps” are on the histogram?)_______________________________________________________________________________

! This is part D of what you need to hand in…• Zoom out to Full Extent so you can see the entire map• Make a screen dump of your map project ( you do this by pressing the following buttons at the same

time: Alt+Print Screen) This will copy the currently active Window. Or use the Snipping tool!• Copy it in your Word Document by using Edit > Paste .

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Jumping ahead… some GIS analysis (we will revisit this subject in more detail):

• Make sure no layers are selected! (see the bottom of page 10 to Unselect).

• In ArcMap, go to Selection > Select by Location. -We now want to know how many earthquakesare within 10 km of a plate boundary….

• Fill out the Select by Location dialog window in the following way:

WORLD MIN MEAN MAX Magnitude Depth


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• Open the Attribute Table (try to remember how…) of the quakes layer. If you forgot, see page 9!• Check the distances of the quakes in relation to the plate boundaries also manually and try the

measurement tool. This is found in your Tools tool box, it looks like a ruler.

• Play around with the different functions and set the tool to kilometers by dragging the arrow nextto the ∑ downward.


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! This is part E of what you need to hand in…From your analysis results, write down the answers to the following questions:

1. Are the earthquakes always located near a plate boundary?• Just a global, visual observation will be enough• -(you can zoom in and out and browse around).

2. How many earthquakes are within 10 km of a plate boundary?• -This answer you get by looking at the selected records of the table behind the quakes2000 layer.

3. What percentage is that of the total earthquakes happening on earth?• -Again, look at the table and figure out the total records.

Write these answers in your Word document

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! This is part F of what you need to hand in…Create a map where you color earthquakes by depth instead of magnitude (Try to remember how, but goback to page 4 if you don’t remember how to do this!) Then use the “Find” tool to locate the island ofTonga, and zoom in so that your scale is at ~1:10,000,000. Then answer the following questions about thecluster of earthquakes you see on your map.

1. What is the name of the cluster of islands north of Tonga, on the opposite side of the plate boundary?

2. What is the general pattern of earthquake depths surrounding Tonga? Do they get deeper to the east orto the west?

3. Knowing what you do about plate tectonics, which plate is being subducted here, and which direction issubduction occurring (to the east or to the west?)

Add these answers to your Word Document

SAVE YOUR FILES ON YOUR MEMORY STICK! Covert your Word doc to a PDF and submit your completed assignment in Canvas to:

GEOL3050-001>Assignments>Exercise 2: Mapping Seismic Activity

Summary: You have done the following procedures in this exercise, try to remember this: • Add Data to a map document (ArcMap) -Know where the Table of Contents and the Data View are

in ArcMap.• Turn layers on and off. Select and deselect layers. Switch the order of layers.• Introduction to changing the symbology of Layers.• Use the Identify tool to get information on individual features.• Look at the Table behind Layers.• Calculate Statistics from layers.

Exercise inspired by-, and dataset derived from: MAPPING THE ENVIRONMENT © 2002 Missouri Botanical Garden Portions © Environmental Systems Research Institute All Rights Reserved Teachers May Photocopy These Modules For Instructional Use.

exercise 2 mapping seismic...

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