-Thomas M. Boyd, Colorado School of Mines, Golden, Colorado

*Published in, The Leading Edge, July 1997 pages 1039 - 1043.

Imagine you are approached by a housing developer interested in identifying the possible extent of a hazard underlying a planned development. She explains that at the turn-of-the-century extensive subsurface coal mining was conducted in and around an area undergoing a recent housing boom. Some of these mines ventured close enough to the surface that in 1896 a mine adit was flooded, killing a dozen miners after it collapsed under a nearby stream. She asks for your advice concerning the possibility of using geophysical methods to detect the existence underground tunnels and voids beneath the development site. After asking questions regarding the specifics of the area and the developer's needs and expectations, you suggest that a gravity survey might be the most cost-effective technique for providing the information required to continue the project safely. She invites you to prepare and submit a formal bid on the project.

A situation like this arising in our field is not difficult to imagine, particularly for those involved in environmental and engineering geophysics. Now imagine that you are eighteen, you are trying to complete your undergraduate degree in a field other than geophysics, and you are working through scenarios such as this to complete the only geophysics course required in your curriculum.

We will describe a World Wide Web-based cross-disciplinary course built on the use of hypothetical scenarios like that described above to teach the fundamentals of geophysical exploration. We are currently using this course to teach junior-level geologists and petroleum engineers at the Colorado School of Mines (CSM). All of the materials described in this article are available to anyone at http://www.mines.edu/fs_home/tboyd/GP311. In addition, free distribution volumes can be made available for remote installation by contacting the authors. Before discussing the details of the course materials, background information and motivation is necessary to place these materials in their appropriate context.

Teaching Geophysics

Traditionally, geophysics is taught to non-majors in the same environment and with the same emphasis, albeit at a lower level, as it is taught to students majoring in geophysics. We generally use a lecture-based format and focus on the physics of the phenomenon being observed, its mathematical description, and the mathematics of data processing and interpretation. The usual approach is to derive basic equations describing the physics, discuss how the phenomenon is related to targets of interest, develop mathematical processes for removing noise and enhancing signal, and then describe how the measurements can be used to infer something useful about the subsurface.

Although this approach may be appropriate for students majoring in geophysics, it does not emphasize what the end-users of geophysical observations and interpretations need to know. Rather than having a detailed understanding of the mathematical underpinnings of geophysics, the end users (geologists, engineers, lawyers, etc.) need to know how geophysics should be done and what can be expected of the results. To put it another way, non-specialists need to understand how specialists reach decisions and what decisions can and cannot be supported by the observations. Why should we be concerned with how geophysics is taught to non-specialists: as long as we continue to graduate top-quality geophysicists shouldn't the value of our contribution to understanding the Earth's interior be self evident? Experience shows that it is not. For better or worse, a geophysicist is almost always a member of a multi-disciplinary team assigned to solve some tangible problem. Other team members can have little innate appreciation of what geophysics can do to help solve the problem, how the various geophysical approaches can be applied, or what the limitations are on interpretations derived from applicable geophysical methods. To insure that the geophysical methods are well represented in this process, it behooves us to begin to develop educational materials that are aimed at delivering, both efficiently and effectively, the appropriate knowledge to non-specialists.

The SEG Multi-disciplinary Initiative

Recognizing the importance of addressing the multi-disciplinary challenges that lie ahead, in 1994, mainly through the guidance and vision of Bob Graebner, the SEG Foundation provided support to the Colorado School of Mines (CSM) for the Multi-Disciplinary Initiative. Although this initiative did not set out to focus on educational issues, it quickly became apparent that the development of sound multi-disciplinary educational practices represented a real need within the earth sciences that geophysicists could begin to address in a meaningful way.

For the problem of teaching non-specialists about geophysics, we asked what better way to convey the essence of geophysics to other professionals than by having them design geophysical surveys, collect data, process these data, and interpret the resulting observations? That is, students would learn the fundamentals of geophysics by doing geophysics.

This learning-by-doing philosophy is certainly not new. Many programs, such as the EPICS (Engineering Practices Introductory Course Sequence) program at the Colorado School of Mines, senior thesis programs used at many universities, apprenticeships and intern programs, and the extensive on-the-job training programs offered by many of the major petroleum companies incorporate aspects of this approach.

One of the more commonly used learning-by-doing approach involves work with case studies. In a case study, students follow a sequence of decisions through a real-world problem applying knowledge gained elsewhere to the specific circumstances of the problem. Case studies allow students to begin to understand the decision-making process involved in applying an academic specialty to real-world problems and to begin to understand the larger ramifications of decisions made within a particular specialty to the problem at large. A limitation of the traditional case-study approach, however, is that students usually cannot take different decision paths through the case. Because of this, it is difficult for students to develop an intuitive understanding of the physical principles underlying the case and explore how different decisions at different points could lead to different outcomes.

Under the SEG's Multi-Disciplinary Initiative, we have been developing and implementing a generalization of the case-study approach that we call the interactive case study. An interactive case study allows students efficient control over all of the important decisions, enabling ready analysis of the implications of alternative decisions. For example when considering geophysical exploration, students control the relevant survey design parameters used in the acquisition of the data, they control decisions regarding the processing of the data, and they interpret the results. Thus, students are not locked into a design and interpretation chosen by someone else. For this to be effective, however, we needed to develop and provide students a friendly learning environment that includes the tools necessary for them to make the relevant decisions at all phases of the case. Modern computing and networking technologies make it possible to implement and distribute this learning environment and tools to a wide audience. The simple premise of the interactive case study has formed the basis for the development, implementation, and distribution of a learning environment for the teaching of geophysical exploration. This environment, including case descriptions, background information, tools for assessing survey design, tools for acquiring data, and tools for processing and interpreting these observations, is currently available to anyone with access to the World Wide Web. Over the past year, we have begun using this environment to teach the essence of geophysical exploration to students majoring in geology and civil engineering at the Colorado School of Mines (Figure 1).

Introduction of Geophysical Exploration

The introductory course that we have developed is divided into four modules, one each on the use of gravity, magnetic, DC resistivity, and refraction seismic observations. Each module consists of two main subsections: lecture notes and the interactive case study. Each module requires approximately 24 hours for students at CSM to complete.

The lecture notes, are presented in a hyper-text manner as a series of short WWW pages complete with graphics and links to outside resources. Our implementation allows students to access the material in any of three ways. The first, and from our standpoint most preferable, method incorporates the use of hyper-links to the appropriate lecture notes directly from the case study. Thus, students can start with the case study and in a relatively seamless way, refer to the notes as information is needed to solve the problem. Additionally, the lecture notes are indexed on an outline Web page. Using this page, students can browse those notes containing material in which they are interested or in which they feel some deficiency. This mechanism is provided mainly for those with some background in the material, but who feel a need to review specifics. Finally, students feeling most comfortable in a traditional lecture environment can move sequentially through the notes before becoming involved in the case study. In principle, this latter method is equivalent to presenting a series of lectures on each geophysical method and then doing laboratory exercises to reinforce the concepts described in the notes (Figure 2).

To complete each module, students must respond to a request for bid (RFB). The RFB presents a problem to be addressed by use of a specific geophysical method. Students are asked to respond to the RFB by submitting a proposal that includes a geophysical survey design, a discussion of geophysical noise relevant to the particular survey, estimates of the geological sources of signal that would and would not be detected by the survey, and estimates of the cost of completing and interpreting data from the survey (Figure 3).

In designing their geophysical surveys, students are provided Java-based Web scripts that allow them to model the geophysical response over geologic structures relevant to the particular RFB (Figure 4). The modeling script generates synthetic observations over simple geological models. Using the forward modeling script and estimates of the cost required to perform each step of the survey, students determine optimal survey parameters for the particular problem, in the sense of survey resolution versus survey cost. Because the optimal survey is defined in terms of a rather nebulous cost-benefit trade-off, different participants rarely define surveys based on the same set of parameters. We actively encourage students to try different survey designs. Whatever design chosen, however, it must be justified to the hypothetical client in the formal bid that is submitted in response to the RFB.

After designing the geophysical survey, the parameters defining each student's survey can be entered into a WWW page and students immediately receive a data set that includes random and systematic noises unique to their particular survey. Students are then guided through a data-reduction procedure using relatively simple spreadsheet manipulations. Upon completing the data reduction, students can finally download a modeling script that allows them to interpret their reduced data by superimposing model computations on the data set. A final report is submitted and includes their preferred solution, uncertainty estimates, a discussion of other interpretations that could fit the geophysical observations and reasons why these other solutions are not preferred.

The data sets collected by the students are remarkably diverse (Figure 5). Although all are collected over the same geologic structure, each is obtained with a different set of survey design parameters. For the data shown here, the relevant parameters include station spacing (Dx) and base station repeat time (Dt). In the top example, survey cost was minimized by using a survey with a relatively large station spacing (10 m). As a result, the resulting geophysical anomaly is poorly defined. In the middle example, survey cost was minimized by increasing the base-station repeat time. The resulting reduced data set is heavily contaminated with earth tides so that the observed anomaly is highly asymmetric, even though the geologic model from which the observations were generated, a simple tunnel, should have produced a symmetric anomaly. The bottom data set represents what the students, after examining data derived from a number of survey designs, thought to be the optimal data set. Although more expensive surveys were designed (one cost over $250,000) students readily discovered that the minimal increase in information content did not justify increased costs once survey costs topped about $25,000.

As you may have suspected, the data sets that the students are analyzing are simulated rather than actually obtained in the field. The use of simulated versus field data has several advantages. First, it allows for the interactive nature of the program. Without simulating data from a geologic model for the students to interpret, students would be unable, in a timely fashion, to collect data multiple times over the same survey site. Thus, if students were required to collect real observations, the comparisons and subsequent conclusions reached from examining data sets would be difficult to implement. The ability of students to look at data from the same site collected with different survey designs allows them to develop an intuitive understanding of the underlying physics, the problems associated with noise, and the economic trade-offs associated with all investigations. Second, because all of the observations are derived from a model, interpretations can be compared directly with ground truth. Thus, even introductory-level students can grasp abstract concepts such as model equivalences and parameter uncertainties. Finally, by using simulations we are able to customize the program by simply swapping simulations. For example, less complex simulations can be used for novice students while more complex simulations can be used for more advanced students.

While completing the above tasks, students are required to codify the rules of manual inversion. We specify that these rules be presented in the form of if-then statements that are included in an appendix to the proposal. When discussing gravity surveys, for example, one of the if-then rules that students would need to define is how the shape and amplitude of the observed anomaly would change if the target of interest is moved to greater depth. The goal of this requirement is to develop an intuitive understanding of the underlying physics, which is more commonly described through mathematical expressions, and to provide a series of rules that students use to interpret and model their reduced observations.

Interactive Case Studies at CSM, and What's Next?

We are teaching our introduction to exploration geophysics course for non-majors (juniors majoring in geology and engineering) based on the interactive case study approach. The interactive case studies form the core of the course; they are not simply used as laboratory assignments that supplement a traditional lecture-based course. In fact, we don't present any formal lectures in this class. Instead we provide students with a schedule of completion dates for specific assignments, direct them to the on-line resources, and meet with them regularly (six hours a week) to answer questions.

Student feedback on this course has been generally positive. Our students seem to thrive on being in control of a project, making decisions that will determine the outcome of the project, and working with data they have generated. Invariably our students describe spending as much as twice as much time on the course as we had estimated necessary. When asked why they spent so much time on the course, by-and-large students say they have chosen to spend this extra time not because they believe it necessary to get an acceptable grade, but because they want to produce better results than those of anyone else in the course. What we've rediscovered is that our students are highly competitive. The interactive, Web-based course has simply tapped into this competitiveness and focused it toward learning about geophysics.

As teachers, it is very exciting to watch students new to the field attack geophysical problems and rapidly progress in their level of sophistication and understanding of the inherent challenges in applying geophysics to real-world problems. Nevertheless, although the interactive case-study approach appears to be effective in promoting inter-disciplinary education, we have much to learn about how to facilitate effective learning at a distance.

The materials we have developed are accessible to students outside of CSM. Anyone with World Wide Web access can get these materials at http://www.mines.edu/fs_home/tboyd/GP311. Try them yourself. To use these materials, you must have access to the World Wide Web and you must be able to send and receive e-mail. In addition, you must have access to several pieces of commercially-available software that are not provided at this Web site. These include any of the commonly available Web browsers (Netscape, Internet Explorer, etc.), a spreadsheet program (Lotus 1-2-3, Excel, etc.), and word processor.

The introductory geophysics course described in this article, although addressing a concrete need on the CSM campus, was really designed as a prototype of what could be developed and distributed using currently available computing and networking technology. We are currently pursuing the development of materials based on this prototype to address the larger concerns of earth-science education at all levels; K-12, undergraduate, and continuing education. At the K-12 level we have secured funding from the state of Colorado to develop web-based materials that would allow high-school students to explore different science and engineering career options. At the same time demonstrating proficiency in a variety of technical subjects, such as calculus, chemistry, and computer science, students might be able to place out of introductory college courses. At the undergraduate level, the American Geological Institute (AGI) foundation has agreed to support this effort and we, along with the AGI, Texas A&M, and the University of Texas, have prepared and submitted proposals to the National Science Foundation to support the development and assessment of additional earth science modules distributed over the Web. On the continuing education front, we are working with the SEG, AAPG, SWLA, and SPE to develop, and implement a reservoir exploration and development simulation for training of multi-disciplinary team members.

Although, we are exploring a variety of avenues that expand on the work completed thus far and a variety of means for supporting these future efforts, professional societies can, and should, play a key role in this continued development. In addition to providing access to much of the technical expertise on which these materials rest, professional societies such as the SEG can help to develop and encourage community support for projects such as this. In supporting the development of the prototype course, the SEG has established itself on the vanguard of distributed, interactive course-ware development. Other professional societies have begun to look at what has been done under the auspices of the SEG and asked how they can participate. The continued leadership shown by the SEG will be paramount for expanding upon our early successes.