Groundwater Depth and Fracture Pattern Determination
Lawrence L. Malinconico
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Learning to use the resistivity methodology for both vertical profiling and horizontal mapping.
Undergraduate course in applied geophysics
Designed for a geophysics course
Skills and concepts that students must have mastered
Understanding about the workings of spreadsheets and charting. They will have been exposed to the concepts related to shallow resistivity surveys.
How the activity is situated in the course
This is a stand alone exercise that is part of the field portion of the course. The students are divided up into manageable groups and each group conducts their own field survey. Each individual student is then responsible for the submission of a project report.
Content/concepts goals for this activity
The objective of this project is to expose the students to the field methods used in resistivity surveying. They conduct both a vertical sounding as well as a mapping application. The only difference with this exercise and a true mapping application is that they stay in one place and look for variations in the resistivity with magnetic bearing.
Higher order thinking skills goals for this activity
The analysis and interpretation requires them to use the collected geophysical data to measure not just the level of the groundwater table, but use the existence of groundwater in the rocks and the variance of the resistivity to interpret local structure.
Other skills goals for this activity
Working as a team
Description of the activity/assignment
Working in teams, the students begin by conducting a vertical resistivty sounding to determine the depth to the water table. This can be checked because the survey is done in the middle of an existing well field. Using the depth determined, the students then conduct the equivalent of horizontal resistivity survey using a fixed "a" spacing. Instead of making a map they collect data at 10-degree intervals rotating the array around a central point. This provides them with information about how the resistivity varies with magnetic bearing and they then have to relate that to an interpretation of the local structure (fracture patterns). Each student has to submit an individual report which includes an interpretation of the data.
Uses geophysics to solve problems in other fields
Determining whether students have met the goals
Various values are assigned to each portion of the project. These are shown on the included assignment sheet.
More information about assessment tools and techniques.
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