Here are some equations that you may or may not find useful for some of the problems.

(some equations were given, don’t have them on this file though. They were cut and pasted from the text, without explanation of the symbols — you at least need to recognize that much)

1. You own a small geophysical consulting company and have been awarded a contract to perform a magnetics survey to look for some prehistoric trash pits. The pits are thought to be approximately 10 m x 10 m, and are thought to be located somewhere on a 150 m by 150 m property. You have two inexperienced helpers who will do all of the field work. Tell them exactly what to do in the field (you will be the one to interpret all the data later, but you won’t go into the field with them).

2. Your company has now secured a contract to determine water resources (depth to and extent of a buried aquifer) on a ranch. What geophysical techniques will you use and why? You are on a limited budget so cannot use more than two different techniques.

3. Drift corrections are important for both magnetic and gravity surveys. Describe what the major sources of ‘drift’ are in magnetics studies and in gravity studies. How do you make a drift correction? What do you have to do in the field?

4. Your company has now obtained a contract to find an abandoned mine shaft. What techniques will you use? Describe your field procedure.

5. While conducting a ground penetrating radar survey across a concrete dam, you see a strong reflection at 5 nanoseconds (ns) two-way time. Approximately what depth does this correspond to? Show your work and state all assumptions.

6. What is the common midpoint (CMP) method of seismic reflection and why is it useful?

7. Describe the difference between seismic reflection and seismic refraction, and discuss advantages and disadvantages of each for determining subsurface structure.

8. Describe the difference between electrical resistivity and electromagnetic (e.g., EM31) field techniques, and discuss advantages and disadvantages of each for determining subsurface structure.

9. Sketch an approximate apparent resistivity curve that would be generated the following layered structure, shown in cross section. Describe the possible geology that this might represent.

10. Describe possible places where gravity surveys would be useful.

11. Gravity is more sensitive to latitude than to longitude on the Earth. Why?

12. (10 points) Interpret the following refraction seismic record section. What possible geologic structure might this represent? If you wanted to find out if this structure were dipping what additional field work would be needed? (use attached graph paper if needed)