Digital Analysis of Geophysical Signals and Waves (DAGSAW)/Filtering
George R. Jiracek
San Diego State University/Department of Geological Sciences
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Filtering is one of the most important steps in geophysical data recording and processing since it is present in all geophysical analysis. Filtering is explained in the Digital Analysis of Geophysical Signals and Waves (DAGSAW) web site using animations in space, time and frequency domains.
Used with NSF-sponsored research experiences for undergraduates (REUs), upper division course in geophysics field methods, and an upper division-graduate course in geophysical analysis. Designed for a geophysics course
Skills and concepts that students must have mastered
Undergraduate physics and mathematics through differential and integral calculus. A course in geophysics is desirable but not required.
How the activity is situated in the course
The Digital Analysis of Geophysical Signals and Waves (DAGSAW) web site is used as introductory material at SAGE (Summer of Applied Geophysical Experience) for REU students. It is also used in the sequence of material taught in geophysics field methods and geophysical analysis courses at San Diego State University.
Content/concepts goals for this activity
Understanding filtering as a continuous and discrete convolution operation in space and time domains, and as a multiplication of complex functions in the frequency domain.
Higher order thinking skills goals for this activity
Filtering as a tool to understand the analysis and modeling of geophysical data. Writing filtering programs with MATLAB.
Other skills goals for this activity
Report writing using actual geophysical data.
Description of the activity/assignment
Students use the concept of filtering as a "black box" input-output operation in either space, time, or frequency domains to develop and use practical geophysical filters such as pass bands, derivatives, integration, and upward/downward continuation of gravity and magnetic geophysical data. Addresses student fear of quantitative aspect and/or inadequate quantitative skills Addresses student misconceptions
Determining whether students have met the goals
Several years of using the attached 25-question quiz given before and after using the Digital Analysis of Geophysical Signals and Waves (DAGSAW) web site during a single morning session with undergraduate students has revealed an improvement of student test scores by an average of ~100%.
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