Scorpions as Seismologists
Laura Reiser Wetzel
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Students investigate how seismologists and scorpions use wave travel times to locate sources of movement. The primary strength of this exercise is that it links geophysics and biology to enhance interest for non-geology majors.
This exercise if for an introductory oceanography or geology course for undergraduates.
Designed for an introductory geology course
Skills and concepts that students must have mastered
To complete this activity, students need to be able to do simple arithmetic and plot points on a graph. The write-up describes all tasks in detail, including how to calculate the slope of a line.
How the activity is situated in the course
I use this activity as part of a geophysics lab in my Introduction to Marine Science course. I introduce geophysical concepts during the lab period, so it may be used at any point during the semester. As written, it could be used as an in-class activity, an in-lab activity, or a homework assignment.
Content/concepts goals for this activity
- To show how scorpions and seismologists use similar methods to locate wave sources.
- To create graphs relating distance and time (travel-time curves).
- To use the constructed time-travel graphs to locate seismic sources using triangulation.
- To introduce the concepts of forward and inverse problems.
Higher order thinking skills goals for this activity
Students must analyze a simple dataset.
Other skills goals for this activity
Description of the activity/assignment
In this exercise, students investigate how desert scorpions locate their prey using a method similar to how seismologists locate earthquakes. The scorpion has specialized sensors in its feet to detect P and Rayleigh waves transmitted through sand. First, students draw waves spreading out from a walking spider like ripples in a pond. In this forward problem, students calculate the wave travel times through sand, create travel-time curves, and calculate the slopes of the lines. Next, in the inverse problem, students are given the Rayleigh minus P times and must use their travel-time curves to determine the distance from the spider to the scorpion. Finally, students draw circles on a map of the scorpion's legs, thereby using triangulation to determine the spider's location.
Has minimal/no quantitative component
Uses geophysics to solve problems in other fields
Determining whether students have met the goals
Students complete all of their work within the lab write-up and their answers are submitted for grading.
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