SIGkit (Software for Introductory Geophysics toolkit) for modelling and visualization of data

Charly Bank, University of Toronto

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Summary

Predicting what geophysical data may look like and making basic inferences from data are critical learning outcomes of introductory geophysics courses whether they happen in a classroom or in a field setting. This software and associated set of teaching activities allows students taking introductory geophysics courses to engage with geophysical models and data through modelling, visualization, and simple analysis of field data.

Learning outcomes that are common for the set (separate activities for gravimetry, magnetometry, resistivity, electromagnetics, ground-penetrating radar, and seismic refraction) are that students will be able to
- explain key concepts, including the relationship between parameters used to describe an object and geophysical data,
- estimate physical parameters for an object (and recognize non-uniqueness of solutions), and
- match a synthetic model to real data.

To our knowledge this toolkit provides the first teaching software that brings together various methods and corresponding data sets into a comprehensive learning software. The activities in their current form are based on a collection of MATLAB scripts; ie, they require students to have access to MATLAB.

Context

Audience

The activities are intended for introductory geophysics courses focussed on near-surface investigations (exploration, environmental, archaeological) as well as geophysics field courses.

Skills and concepts that students must have mastered

Familiarity with MATLAB is not required to run the software, however the instructor should be familiar with MATLAB to help students get started.

How the activity is situated in the course

Introductory geophysics courses typically expose students to various methods. This activity offers separate activity sheets for each method (gravimetry, magnetometry, resistivity, electromagnetics, ground-penetrating radar, and seismic refraction) that can be selected to introduce the method before class (eg, if you are using a flipped teaching approach) or at the start of the class, to reinforce theory, to predict data, and to analyze data. Parts of the activity can be assigned for out-of-class work. The software has been used for in-class testing, and for selecting survey parameters in field courses.

Goals

Content/concepts goals for this activity

Key concepts students engage with in this activity are:
- gravity: effect of depth and density on a gravity anomaly of a 2D object
- magnetics: magnetic anomaly for a 2D object and parameters (magnetic latitude, profile azimuth, height of sensor, total field intensity and gradient, induced and remanent magnetization), allows for extraction of profile from a map
- resistivity: resistivity sounding curve, apparent versus true resistivity, equivalent layer principle
- electromagnetics: apparent conductivities, vertical and horizontal coils (activity incomplete because no data set included)
- GPR: two-way time versus depth, imaging artefacts (diffraction hyperbolae, bow ties)
- seismic refraction: travel-time curves for horizontal 2-layer case, picking first breaks, hidden layers

Higher order thinking skills goals for this activity

The set of activities encourages students to
- predict data for given model parameter,
- test predictions against real data,
- analyze field data, including self-collected data, and
- recognize the non-uniqueness of geophysical models and interpretation.

Other skills goals for this activity

other skills this activity may improve:
- working in groups
- arguing their case (eg, why to use a certain setup for a field survey)

Description and Teaching Materials

The activity includes a set of handouts for students explaining how to run the software, engaging them in a guided tour of key concepts for the 6 methods, and allowing them to explore real data. The software is provided as a set of scripts in a directory which needs to be unzipped. The computer students want to run these scripts from needs to have MATLAB installed.

activity handouts (Acrobat (PDF) 568kB Apr3 19)

SIGkit_noGUI.zip (Zip Archive 5.4MB Apr3 19)

Teaching Notes and Tips

Many students seem to be scared of MATLAB; the longer-term goal of the SIGkit team is to make this into a GUI. Until then it is beneficial if the instructor or teaching assistant shows how to use the activity at the start. I also have found it helpful to allow students to work in small teams; for example by having individual students run models with different parameters and then have small groups compare their results.

Instructors wishing to see results for the example data please email me (provide a link to your institutional website) and I will forward you that information.

Assessment

So far I have discussed the activities in class, and students may submit short answers to the questions; or finish an activity (obtain a matching model to the data) as a homework. I have allowed students to use SIGkit to design a survey (for given parameters) or analyze a data set in an in-class test often in small teams. In the field course the software has been used by students to visualize and analyze data for their reports.

Please let us know of any errors, confusions, and suggestions for improvement.
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