Modeling Asperities with Spaghetti
Skills and concepts that students must have mastered
How the activity is situated in the course
Content/concepts goals for this activity
- rocks deform in elastic ways
- when significant stress is applied, rocks can undergo brittle deformation
- earthquakes occur when specific sections of a fault fail
- aftershocks are small earthquakes occurring after the primary failure
Higher order thinking skills goals for this activity
Other skills goals for this activity
Description and Teaching Materials
This activity was developed to facilitate student learning with the Aspertity Model. In fault systems, failure on one part of a fault is preceded by elastic deformation of the rocks on either side of the fault. When a fault fails, there are typically adjustments in other sections of the fault that cause aftershocks. In this activity, students observe that as they apply stress to the model fault, the spaghetti will undergo elastic deformation. As the spaghetti fails, it experiences brittle deformation. This failure does not happen to all of the spaghetti concurrently. There are often aftershocks as the students run the physical model multiple times.
We revised the model that was posted on the IRIS.edu website such that there is a 5 mm groove along the fault boundary that allowed the students to better see the elastic deformation of each spaghetti strand. We also added a metal plate with a tongue-and-groove to the back of the wood blocks to help them stay together while students applied stress.
The challenge question relates this model to the real setting where we can observe GPS stations showing the elastic deformation around a fault. We did not expect many students to be able to answer this question, but offered it as a challenge to those with a stronger science background. Prior to this class, students watched the IRIS video: https://www.youtube.com/watch?v=NMNNr2CyekA about subduction and GPS motion. This particular question is credited to M. Brudzinski of Miami University.
The original model and background text for this activity is credited to the Incorporated Research Institutions for Seismology (IRIS.edu). A video and description of the model can be found here: https://www.iris.edu/hq/inclass/lesson/modeling_asperities_on_a_strikeslip_fault_with_spaghetti
Asperity Worksheet (Microsoft Word 2007 (.docx) 542kB May31 17)
Asperity Description (Acrobat (PDF) 1.4MB May31 17)
Asperity Model Construction (Acrobat (PDF) 589kB May31 17)
Asperity Background (Acrobat (PDF) 153kB May31 17)
Teaching Notes and Tips
The attached file includes suggestions for construction of the asperity model. The clamps are relatively expensive at $10 a piece, packaged in sets of 2 clamps. Many hardware stores did not stock a large number of these small clamps, so ordering online was necessary. We used a mixture of whole wheat and regular pasta to accentuate that not all pieces would break at the same time. The pattern of failure was difficult to discern while using one type of pasta.