PHYS/GEOL 406 Homework
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   Homework #1: Due Friday January 30 by 5:10pm

Reading:

  • Sections 6.3.1-6.3.4 (normal gravity and gravity corrections) Note that the sections immediately after this detail further corrections, but the ones I covered in class are the major ones. If/when you need to account for these others, I'm confident you can go back to this book and pick up that information. The concepts are the same.
  • Recall how I spent considerable time in class discussing how you always work with the gravity anomaly dg or Δg.
  • 6.4.2 (base stations are the "baseline" I keep talking about)
  • 6.5.1 (rock densities in Table 6.5)
  • 6.5.2 (gravity of a sphere; complex structures can be modeled as a lot of spheres). Note that the sections after this deal with those other shapes I mentioned in class (vertical cylinders, horizontal cylinders, etc.).
Assignment:
  1. problem 6.5. You do this in real life to judge whether or not your equipment is actually capable of doing the survey you may be asked to do.
  2. problem 6.9. Clearly identify which depth goes with which sphere. Here as always, show your work.
  3. Find the radius of the spheres in problem 6.9 assuming the spheres have the following densities: (1) 3,400 kg/m3 (2) 2,700 kg/m3 (3) 2,900 kg/m3. The background matrix has a density of 2,500 kg/m3.
  4. Assume the gravity anomaly map below shows something that may be modeled as a sphere. Use the gravity anomaly map to do the following:
    a. Make a graph (spreadsheet) of dg vs. x for the line A-A'. On your spreadsheet change those units of miles (ugh!) to km (yay!).
    b. Determine the depth to the center of this body.
    c. Assume the magnitude of the density contrast is 350 kg/m3. Find the radius of this sphere. Click on the image for a larger version that you can print and use to make your transect like we did in the class example. This one is smaller so it can fit in your browser window.

   That's all for homework #2.