Analyzing Fault/Fracture Patterns

Jamie Levine, Whitman College

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Initial Publication Date: June 1, 2012 | Reviewed: January 19, 2015 (see revision history: 2 events)

Summary

During a lab period, students go out in the field to an area that contains at least 2 fault/fracture sets. Students measure orientations of faults and make observations about the relationship between different fault sets. After the field trip, the students compile their field data, plot it on a stereonet and write-up a brief report. In this report students will use their field observations and stereonet patterns to determine whether faults are related or unrelated to each other.

Folds/Faults/Ductile Shear Zones, Joints/Fractures | College Upper (15-16)

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Context

Audience

Upper level structural geology course

Skills and concepts that students must have mastered

It is imperative that students have learned about conjugate faults, fault systems, Coulomb failure and Anderson's Theory of Faulting in class and know how to use a Brunton compass and to plot data on stereonets.

How the activity is situated in the course

This is a stand-alone lab activity done towards the end of the semester. It may require some follow-up for 5-15 minutes in a class period.

Goals

Content/concepts goals for this activity

Relationship between fault sets, Anderson's Theory of Faulting, Coulomb Failure, Collecting field data

Higher order thinking skills goals for this activity

Analysis of data
Deciding between multiple hypotheses

Skills goals for this activity

Distinguishing between observations and interpretations
Making measurements with a Brunton compass
Interpreting stereonet data
Writing

Description and Teaching Materials

The document titled Conjugate Faults Activity SGT is a set of notes for the instructor on how to run the lab, what students need to know before lab, and some of the goals.

The document titled Structure Field Trip_Conjugate faults is the handout given to the students.

Analyzing Conjugate Fault Patterns (Microsoft Word 25kB May7 12)
Student Handout for Conjugate Fault Assignment (Microsoft Word 25kB May7 12)

Teaching Notes and Tips

When I did this activity in the past, I found that students recognized faults in the field as conjugate, but when they plotted their data on the stereonet, they failed to see a pattern. Consequently in their write-ups they interpreted the faults as random. I suggest taking 10-15 minutes in class to show some examples of stereonet data from recent issues of the Journal of Structural Geology (or other journals) and discussing causes of scatter in the data and interpreting stereonet patterns. It is also important to have discussed in class either prior to the assignment or after, what types of patterns we would expect on a stereonet for conjugate faults, unrelated faults, etc.

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Assessment

This assignment is assessed primarily on their write-up of the field trip. I place emphasis on whether students have separated observations from interpretations and whether they have used their field data and the stereonet data together to achieve a coherent picture.