Spatial Visualization Strategies for Improving Student Understanding of the Elastic Rebound Theory of Earthquakes
Summary
In this study we focus on the concept of elastic rebound, as recent studies have identified that student understanding of elastic rebound and how it causes earthquakes is often incomplete (Dolphin and Benoit, 2016; Hubenthal, 2018). A variety of different models of elastic rebound have been proposed for instruction due to the difficulty in creating a visualization of the actual process that operates on faults due to the wide range of scales involved. For example, rocks near a fault are bent, on the order of a few meters displacement near the fault relative to rocks far from the fault, but this bending can occur over tens of kilometers of distance. In addition, the bending near active faults builds up gradually over tens to hundreds of years, but when an earthquake occurs, the rocks move in a matter of seconds. People typically see only the results of an earthquake, such as the offset of a fence built across a fault, but not the gradual motion that precedes such an earthquake. Students may learn how to characterize faults based on their offset, but have a harder time learning what leads to those offsets, and hence what is the true physical cause of earthquakes.
The increasing precision of geophysical instruments has enabled geoscientists to measure gradual motions along faults in greater detail. One of the most common strategies is to attach a high precision GPS receiver to a rock exposure and then record its daily position over many years using satellite signals to establish its geolocation. When a network of these GPS stations is installed around a fault, the process of rock bending can be observed in the variations of ground motion from near the fault to far away. We hypothesized that realistic imaging of spatial patterns in ground motions over the course of the earthquake cycle can help students understand the elastic rebound concept through visualization of the movement (Brudzinski, 2018). How the spatial patterns in GPS-derived ground motions could be used to help students visualize the elastic rebound concept has not been investigated, so we sought to present variations in ground motion near a fault at multiple points in the elastic rebound process to evaluate whether they support students developing mental models that incorporate the key aspects of elastic rebound: friction on the fault creates locking, rocks bending to accumulate elastic energy, and the earthquake causing the rocks near the fault to catch up with the motions far from the fault.
Context
Audience
This assignment has been deployed at multiple levels of the undergraduate curriculum: 1) an introductory non-majors course, 2) an early majors solid earth course, and 3) upper level Geophysics and Seismology courses.
Skills and concepts that students must have mastered
This assignment does not require prior mastery of geoscience skills and instead seeks to teach the elastic rebound theory for earthquakes in a more comprehensive manner.
How the activity is situated in the course
This assignment is envisioned to occur as a stand along assignment during the earthquake unit of a course.
Goals
Content/concepts goals for this activity
The strategies and associated assessments were designed to help students understand the relationship between pre-earthquake deformations and fault motion and to flexibly reason about motion from a variety of reference frames. To help students develop a model of how earthquake motions related to pre-earthquake ground motions, we asked students to reason about how the ground would move before, during and after a quake, allowing them to make predictions before we provided feedback. Students are given multiple opportunities to make predictions and get feedback. We varied the fault geometry, the frame of reference for the motions, and whether students were given ground displacement or velocity. Frame of reference was varied by adjusting where ground motion was zero relative to the fault.
Higher order thinking skills goals for this activity
This assignment is focused on spatial reasoning skills.
Other skills goals for this activity
The repetition of this assignment was designed to offer an opportunity to develop flexibility in using different frames of reference for motion, as in practice different reference frames are used frequently in plate tectonics and with GPS data in particular (e.g., Cox & Hart, 1991; Freymueller, 2021).
Description and Teaching Materials
The assignment has been constructed to utilize two types of map (overhead) view spatial representation of the elastic rebound patterns around a right-lateral strike slip fault at different times of the earthquake cycle: a fence that bends and breaks over time and GPS vectors showing the surface velocity at a given time. To help students improve their mental models we employed the principle of spatial feedback in the context of worked examples that arose from design science work in the GET-Spatial collaborative network (Davatzes et al., 2018; https://serc.carleton.edu/getspatial). To provide support for students who did not have a mental model, we specifically developed a set of narrated animations showing spatial patterns of bending and associated velocity vectors over time to illustrate the key spatial and temporal patterns associated with the elastic rebound process.
GIFT format file for Elastic Rebound Assignment (Text File 55kB Apr27 23)
Teaching Notes and Tips
This assignment was constructed in the Moodle learning management system, and has been exported in the GIFT format. More information about the syntax of this format can be found here: https://docs.moodle.org/en/GIFT_format
Assessment
This assignment is automatically graded by the learning management system, with the exception of two questions that ask the students to describe the spatial patterns they observe in the different animations.
References and Resources
This assignment was developed as part of a research project and a manuscript for peer review is currently being finalized. In the meantime, here are current references that provide some additional detail about this project:
Brudzinski, M. R., Shipley, T. (2019). An Evaluation of Spatial Visualization Strategies for Improving Student Understanding of the Elastic Rebound Theory of Earthquakes, American Geophysical Union Fall Meeting Abstract ED21C-1044, San Fran.
Brudzinski M. R., Using GPS velocity vectors to illustrate elastic rebound, In The Trenches, 8 (1), https://www.nagt.org/nagt/publications/trenches/v8-n1/196290.html, 2018.