This is the 2001 midterm. Note that the 2002 midterm will only cover seismics.

 

JGP438F – MIDTERM – 25 OCTOBER 2001

Try all 4 questions. They are NOT of equal value. Write answers in the booklet provided. No aids allowed. The test totals 20 points.

  1. (6 points) The following processes affect propagating seismic waves. In about a sentence each, or with an adequately labelled diagram, describe each of them.
    1. Reflection
    2. Refraction
    3. Critical Refraction
    4. Diffraction
    5. Attenuation
    6. Mode conversion
  2. (4 points) Describe the basic principles of filtering. Give examples of two types of filters used in seismic data processing.
  3. (6 points) Sketch a seismic trace gather obtained over an Earth with a single interface at a depth of about 1 km, in which there is a direct wave, ground roll, a refracted arrival from the interface, a first reflection from the interface, a multiple reflection from the interface, and a shear wave reflection from the interface. Label these events. No text is required here other than good labels.
  4. ( 4 points) Describe the operating principle of at least two distinct types of gravimeters (the principle whereby the gravity value is realized as a measurable quantity, not the details of construction). Use sketch diagrams if this helps you.