Give a formula which relates wavelength
Distinguish between a seismograph and a seismogram.
Explain in very simple terms how a seismograph works.
What are the 4 principle types of waves produced by an
Which of these are body waves?
Which are surface waves?
Which waves are the fastest? Gives equations for the
velocities of P-waves and S-waves.
What is the most important factor in determining velocity in
What are SV and SH waves?
Why can't S-waves travel through liquid (give a mathematical
Show mathematically why P-waves are faster than S-waves.
Describe the motion of a particle of rock as each of the four
principle seismic waves passes.
What is the effect of depth of focus on the production of
What happens when a seismic wave meets a surface of
discontinuity within the Earth?
What is the relation between the angle of reflection and the
angle of incidence?
Give Snell's Law.
What happens to a wave when it meets a surface of
discontinuity at the critical angle?
Be able to trace the paths of earthquake waves such as PS, PcS,
PKP, PKIKP, pPcP, etc.
List some reflected and/or refracted waves which might be
mistaken on seismograms for surface waves and for aftershocks.
Explain how the epicenter of an earthquake can be located.
How do we know that the upper mantle is partially molten?
At what depths do major discontinuities exist within the
Earth? What are the names of these discontinuities?
Name 2 minor discontinuities in the Earth.
What are the two methods commonly used in seismic prospecting?
Which is most often used? Which gives the most information?
What sources of energy are most often used in seismic
Describe in detail how refraction profiles would be produced,
and what information could be obtained from them.
What kind of time/distance graph would be produced where
velocity increases continuously with depth?
What kind of graph would be produced where velocity first
increases continuously with depth and then abruptly changes?
What kind of graph would be obtained if a seismic profile was
taken perpendicular to the strike of a vertical fault?
How can the throw of the fault be determined?
List 3 factors which help determine seismic wave velocity.
How does one recognize a reflecting horizon on seismograms?
How can the depth to a reflecting horizon be determined?
How can the dip of a reflecting horizon be determined?
What is seismic/earthquake tomography? What information can it
List and discuss possible geophysical properties which may be
indicators of forthcoming earthquakes.
modulus of rigidity
QUESTIONS ON RESISTIVITY
- Define potential difference. What is the difference in potential
difference and voltage? What is the unit of voltage?
- apparent resistivity
- What are the units for resistivity? Give a formula for resistance.
- What is the most important thing that determines conductivities of rocks?
- When a current is passed through the ground, what effects do bodies of
different conductivity produce?
- How can you map the electric field produced when a current is passed through
- Define equipotential lines.
- What happens to equipotential lines in the presence of a good conductor? in
the presence of a good insulator?
- How can you study vertical differences in resistivity in the Earth?
- Write a good original
question to add to this list.
- What is the approximate value for the acceleration of gravity?
- How do we know that the interior of the Earth must be composed of rocks
denser than those on the Earth's surface?
- What causes the Earth's oblateness?
- What is the name of the formula used to calculate the theoretical value of
"g" at any latitude?
- In what two ways may one measure the actual value of g at a particular
- What is a gravity anomaly? a positive gravity anomaly? a negative gravity
- Name the reasons why the actual value of g measured at a particular place is
not the same as the theoretical value.
- What corrections are applied to:
- "correct" actual values of g to remove that portion due to the mass
between sea level and the elevation at which g was measured,
- correct actual values of g to remove the effects of nearby mountains and
- correct actual values of g to sea level?
- Free Air anomaly
- Bouguer anomaly
- Which of the three most commonly applied corrections is the least important
and is often ignored?
If not ignored, how is the corrections usually
made? Why is the topographic correction always added to the measured value?
- What are the characteristic values for Bouguer Anomalies in the following
- mountain regions
- continental shields
- How are positive anomalies produced? negative anomalies?
- Describe Pratt's and Airy's concepts of isostasy.
Which is probably correct?
- What is another name for small scale anomalies which remain after regional
anomalies are removed?
- Outline the procedure for interpreting gravity anomalies.
- What kinds of anomalies (sign and shape) would be produced by the following
- salt domes
- sedimentary basin
- mass of granite
- ultramafic mass
- buried ridges and valleys
- oceanic trenches
- oceanic ridges
- buried stream channel
- continental crust/oceanic crust boundary
- What is the "International Gravity Formula"? What
does each term in the definition signify? Explain what the formula is used
- Define Free Air, simple Bouguer and complete Bouguer
anomalies. What is the significance of each term in the definitions?
- Explain how the three anomalies behave on a regional
scale and on a local scale. Which anomaly is preferred for exploration?
- Explain several ways to separate regional and
residual gravity fields. What are the advantages and disadvantages of each
method? In what circumstances would each be preferred?
- Compare and contrast gravity methods with
other geophysical methods for solving various problems such as...
- Explain how to convert gravity meter readings
into gravity anomalies relative to a base station. What data do you need in
addition to the meter readings?
- Write a good original question to add to this list.
QUESTIONS ON Oceanic Lithosphere
What is the lithosphere? How are its boundaries
defined? On what evidence is its existence based?
How is sea floor topography inferred from studies of
gravity over the ocean?
Is Earth’s mantle beneath the plates liquid or solid?
How deep are the deepest earthquakes at mid-ocean ridges?
At transform faults? At subduction zones?
updated January 5-2005