Exercise: stereographic Projections#
Complete the following exercises using the correct stereonet. Some problems will require answers using hand drawn stereonets and computer generated stereonets. You may use the software to check all answers before submission. All problems should be logically organized and clearly described upon submission.
You will need:
Blank equal angle and area stereonet
1 Thumbtack
tracing paper (take extra sheets)
Work in pencil and erase errors
Stereonet program.
Problem 1#
Plot planes and lines with an equal angle stereonet on separate sheets of tracing paper and with the Stereonet program. Print the Steronet results. On tracing paper and printed results label each plane and pole as 1a, 1b, 1c, etc.
Plotting planes#
Plot each of the following Bed orientations as great circles on the same tracing paper overlay. Label each plane. Be sure you visualize each plane as you plot it!
S25°W, 44°NW
S14°E, 85°SW
N83°W, 43°NE
N72°E, 06°SE
234°, 18°NW
227°, 01°NW
270°, 38°N
000°, 90°E
Plotting Lines#
Plot each of the following lineations (plunge/trend) as points on the tracing paper.
32°, 087°
43°, 217°
12°, N12°E
88°, 092°
86°, 270°
59°, N60°E
59°, S60°E
59°, N60°W
Problem 2#
Plotting poles from planes Plot the following planes as poles on an equal angle stereonet. Complete exercise on one sheet of tracing paper and using the stereonet software. Label all poles a-h on the results. Turn in the tracing paper and printed results.
205°, 44°NW
S14°E, 85°SW
N83°W, 43°NE
072°, 6° SE
234°, 18°NW
040°, 90°SE
270°, 38°N
180 ̊, 90 ̊
Problem 3#
Complete exercise by hand using an equal angle stereonet and with the software. Attach tracing paper and print out software results. Compile all results in an organized manner.
During field mapping, you recorded the trend and plunge of 4 different and overprinted sets of slickenlines. When you sit down to write your report, you find something wrong. Here is the information from your field notes:
Fault Surface Strike/Dip: N39°W, 47°E
Slickenline lineation 1: Plunge/Trend: 47°, N51°E
Slickenline lineation 2: 68°, due N
Slickenline lineation 3: 47°, N51°W
Slickenline lineation 4: 34°, due N
a) Assuming that you recorded the planar attitude of the fault surface correctly, determine which lineation measurements are impossible. In other words, which lineation(s) cannot possibly lie in the specified plane. This time, support your statements with a well constructed stereonet.
b) Assuming the measurement of lineation 1 is correct, what is its rake?
c) Assuming the measurement of lineation 1 is correct, is the fault a strike-slip fault or a dip slip fault?
d) After your last mistake, you return to the outcrop and re-measure the lineations. This time, you get the correct ones from the previous set plus two additional sets. What is the difference in angle (difference in rake) between these two lineations?
Slickenline lineation b1 Plunge/Trend: 11°, N29°W
Slickenline lineation b2 Plunge/Trend: 44°, N29°E
e) Calculating apparent dip from true dip It turns out that your fault is also exposed during excavation of the foundation for the construction of a new building. The excavation wall is vertical and trends N20°W. What is the apparent dip of the fault? Hint: plot both planes and estimate from intersection.
Problem 4#
Calculating true dip from apparent dip Complete exercise with software using an equal angle stereonet. Print results and show calculation on a separate paper. Interesting outcrops of are exposed in the walls created during the excavation done for the foundations. You are asks for the strike and dip of the formation. Unfortunately, you can’t get a good measurement of the strike or dip. Instead, you measure the apparent dip in two vertical walls. What is the true dip of the formation?
Wall 1: Strike: S48°W. Dip: Vertical. Apparent dip of Chert: 23°.
Wall 2: Strike: N55°W, Dip: Vertical. Apparent dip of Chert: 34°.