Exploration and Environmental Geophysics

Jeffrey A. Nunn
,

jeffrey.nunn@gmail.com

Louisiana State University, Baton Rouge
a

University with graduate programs, including doctoral programs

Summary

In the absence of drilling, geophysical exploration methods are the principal means of examining the shallow subsurface. These techniques are non-invasive and relatively inexpensive. The objective of this course is to teach how geophysical properties such as seismic velocity, gravity, resistivity, and attenuation can be used to characterize the subsurface. Emphasis will be on the contrast in physical properties required by each technique and the combination of varied geophysical data (e.g., seismic and electrical methods).

Course URL: http://www.geol.lsu.edu/Faculty/Nunn/gl4062/
Course Size:

15-30

Course Context:

This is an upper level undergraduate or first year graduate level geophysics class. It also attracts some engineering students. Prerequistes are a year of calculus and either structural geology or sedimentology. There is an associated 3 hour laboratory.

Course Goals:

Students should be able to able to interpret a variety of geophysical data (e.g., gravity, seismic, GPR)
Students should be able to design and execute a geophysical survey (e.g., gravity or seismic reflection)
Students should be able to recognize the advantages/limitations of each geophysical technique in terms of how those data were acquired (e.g, common offset versus common depth point seismic data)
Students should be able to recognize the advantage/limitation of geophysical techniques in terms of what contrasts in physical properties it can detect (e.g., seismic reflection cannot distinguish between sand and shale unless their acoustic impedance are different).
Students should be able to select an appropriate geophysical technique to solve a particular problem (e.g., delineate an underground plume of DNAPL).

How course activities and course structure help students achieve these goals:

Each week the students do a different laboratory exercise where they gather and/or interpret geophysical data. They learn how to use the actual equipment. They learn that equipment doesn't always work well. They also learn how to detect and mitigate bad or suspect data. Each week, they turn in a laboratory report which is a primary part of their grade. These exercises are graded and discussed the following week. In addition, there are essay exams in which students must demonstrate that they understand and can apply basic principles of geophysics. Finally, as part of their final project they are given a problem and asked to come up with a solution for their "client".

Skills Goals

writing
oral communication
quantitative abilities
working in groups

How course activities and course structure help students achieve these goals:

This class is approved as a Communication Intensive class at LSU. The laboratory reports are graded for writing ability as well as content. Almost all exercises involve quantitative analysis of geophysical data. I make extensive use of Excel so that students can crunch numbers without having to know a programming language. Students also work in groups for most exercises. In most instances, working in a group is necessary to complete the exercise (e.g., reflection survey). Finally, each student has to give 2 oral presentation during the semester.

Attitudinal Goals

Healthy skepticism

How course activities and course structure help students achieve these goals:

By actually gathering data, students learn where things can go wrong and what a particular technique can and cannot do. Each week, they have to deal with bad data they gathered. Data sets are now available at the click of a mouse. Some are good some are not. I try to teach students how to determine the difference.