Wysocki Farm Refraction Project
University of Massachusetts
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Wysocki Farm refraction project is a lab activity to determine depth to the water table and to bedrock using given seismic refraction data collected on the campus of the University of Massachusetts. Seven shots over one geophone spread allow for detailed modeling of subsurface boundaries.
This lab is used in an upper level Geophysics course in combination with the section on Seismic Refraction.
Designed for a geophysics course
Skills and concepts that students must have mastered
Students must have some introduction to seismic refraction as a process, especially the concept of plotting time-distance graphs and the relationship to seismic velocity.
How the activity is situated in the course
This is the second lab in the seismic refraction section—the first is an outdoor lab collecting some seismic data. This lab then allows them to process and model seismic data. (We sometimes collect enough data in the first lab to use it here instead of the provided data).
Content/concepts goals for this activity
Goals are to determine seismic velocities and depths to boundaries from refraction data.
Higher order thinking skills goals for this activity
Higher order skills goals include conceptual skills (understanding the data set-up and where it came from), data analysis skills (7 seismic lines, each with 12 geophones) and computer modeling skills (manipulation of the data in SIP programs, and generation of sensible models).
Other skills goals for this activity
Other skills include developing skill, patience, and confidence with computer programs, and report writing.
Description of the activity/assignment
The students are challenged to help the University determine if an old farm near campus is a good building site by determining the depth to bedrock and depth to the water table from seismic refraction data. One sting of 12 geophones is used, with 7 different shot (source) points, so 7 data sets are generated. The students take this data, and using SIP programs, plot up time-distance plots, making their best decisions as to how many layers are present and how the layers are represented in the T-D plot. The program will then calculate velocities and depths based on the student input. Decisions need to be made on the "rightness" of their choices from the calculated velocities and times. Corrections can then be made to the assigned times, and (hopefully) better results obtained, until an acceptable model is produced. A report is then written to the University on their findings.
Determining whether students have met the goals
As with many geophysical projects there is no one right answer to this exercise. Student results are compared (usually orally) to see how different students interpreted the data. Written reports are graded, but the group discussion is important to see if they understand the concepts.
More information about assessment tools and techniques.
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