Department of Earth & Atmospheric Sciences
Saint Louis University
Introduction to Earthquakes
Sample Exam Questions 02
These questions are only examples of the types of questions you should be prepared to answer. You should study the notes from the WWW and notes from discussions that we had in class. Note that the word "study" is not the same as the expression "look over". I expect you to have read the notes and thought about the ideas and concepts that we discussed.
The potential essay questions are on another page.
Place a "T" or an "F" or write "true" or "false" in the space provided. Each question is worth 1 point. Be neat, if I can't tell what you wrote, it's wrong.
- A fault is a wide, uniform fracture in rocks.
- Some of the strongest evidence in support of the big bang hypothesis is the electromagnetic hiss pervasive in our part of the universe.
- Continental lithosphere is easy to subduct because its density is so low.
- No earthquake ever caused more than 100,000 deaths.
- Different colors of light are products of electromagnetic waves with different amplitudes.
- Seismic wave speeds are given by a formula that includes an elastic modulus divided by the density.
- The class of scientific information that you find in high school text books is firmly established and never revised.
- We have seismograms generated by most large earthquakes during the last 200 years.
- Seismic waves in Earth follow curved paths because of the curvature of Earth - it's a sphere.
- Two types of plates exist - continental and oceanic, because the plate boundaries follow the edges of continents.
- Primary waves always travel faster than S waves.
- Short-period and long-period seismic recording systems are analogous treble and bass in a sound recording system.
- Richter magnitude is "the" reference for earthquake size, other measures are approximations to Richter's method.
- A ground acceleration of one "g" would not cause much damage.
- Following large earthquakes the intensity of shaking is carefully mapped out using seismograms.
- Dots on maps showing earthquake locations technically show the location of the earthquake focus.
- Because tsunamis travel slowly compared with other seismic waves, we always have time to issue warnings to people in coastal regions susceptible to damage.
- The amplitude of a seismic wave is a measure of the distance between the peaks in one cycle of a vibration.
- Earthquakes almost always are part of a sequences that are composed of foreshocks, the main shock, and aftershocks.
- The regular reversals of Earth's magnetic field are a valuable tool for mapping the age of the ocean floors.
- Elongation of seismic intensity maps is generally a reflection of the decrease of vibration amplitude with distance from the fault.
- Low velocities in the upper mantle are associated with subduction zones.
- As a P-wave travels through a rock the volume remains constant.
- The predominant structure of Earth is a spherical symmetry.
- Although digital seismograms are more convenient for computer analyses, they generally cannot record as large a range of ground shaking as the mechanical-analog systems.
Multiple Choice -write the best answer in the space provided (Each question is worth 2 points).
- Ocean currents move warm water towards the poles and cool water towards the equator. This is an example of
a) Wave propagation b) Convection
c) Conduction d) Elastic deformation
e) All of the above
- An earthquake seismogram is a recording of
a) monochromatic ground vibrations b) sound waves
c) acceleration, pressure, & temperature d) elastic wave vibrations
e) All of the above
- We believe that Earth's outer core is fluid because
a) P-waves pass through it but S waves do not b) P waves do not pass through it
c) Neither P nor S waves pass through it
d) S and P waves speed up as they pass through it
e) P and S waves slow down as they pass through it
- One way that we image the lateral variations in seismic velocity is with
a) CAT scans using x-rays b) Seismic Tomography
c) Heat flow analyses d) Seismic Rebound e) All of the above
- The largest change in seismic wave speed in Earth occurs at
a) The surface b) The Moho
c) The crust-mantle boundary d) The core-mantle boundary
e) All of the above
- Large tsunamis cannot be caused by
a) a large meteorite impact b) a strike-slip faulting earthquake
c) a submarine landslide d) a reverse faulting earthquake e) all of the above
- If Earth's crust is less dense than the planet as a whole, then the interior of the planet must be __________________ than the Earth as a whole
a) less dense as well b) less dense but hotter
c) denser d) denser, but cooler
e) less dense but cooler
- Suppose that you have a container full of 6400 unstable atoms which have a half-life of 12 hours. Three days later, you will have
a) 750 daughter atoms b) 6300 daughter atoms
c) 800 daughter atoms d) 100 daughter atoms
e) No parent atoms, only stable atoms undergo radioactive decay.
- The amount of time it takes a P-wave to travel straight through the planet is about
a) 60 seconds b) 200 seconds
c) 1500 seconds d) 3000 seconds e) one day
- Suppose that the outer core of Earth didn't exist and the mantle extended down to the inner core. What would be the effect on the P-wave shadow zone?
a) It would be smaller b) It would be larger
c) It would increase in some places and decrease in others
d) It would cease to exist because the inner core is solid
- The variation in velocity with radius within the mantle transition zone is a result of
a) Chemical variations from convection b) Temperature variations from convection
c) Temperature variations from conduction
d) Pressure effects on the atomic structure in mantle rocks e) All of the above
- Consider a one-second period P wave traveling through the mantle. Compared to that P-wave's wavelength the upper mantle, the wavelength in the lower mantle is
a) smaller b) larger
c) the same d) dispersed e) refracted
- In a single earthquake the crust moves 3 meters on the boundary of a plate moving 6 cm/yr. How long had elastic strain been building up at this site?
a) 50 years b) 180 years
c) 18 years d) 1.8 years e) 500 years
- Which of the following is not a true statement about seismic wave speeds? It
a) increases with pressure b) increases with temperature
c) depends on rock type d) depends on wave type
e) a through d are all true
- The periodic table is a(n)
a) a chart outlining the history of chemical-element discovery.
b) a chart used to estimate the temperature of stars by their spectra.
c) a chart of elements organized by relative abundance in the universe.
d) a summary of the chemical properties of the elements.
e) All of the above.
- An isotope is
a) an atom with a charge imbalance b) an atom with more protons than electrons
c) the same thing as an ion d) an atom with more electrons than protons
d) All of the above e) None of the above
- Suppose that you flip a coin three times. What are the odds that two or more out of the three tosses are heads?
a) 1 in 8 b) 1 in 3
c) 3 in 8 d) 2 in 3 e) 4 in 8 or 1 in 2
- The key to our success with science is
a) Curiosity b) Mathematics
c) Computers d) Nature's Patterns e) Observation
- The area experiencing high earthquake intensities for a large earthquake is higher in the eastern U. S. than in the western U. S. because
a) A dense population makes it more perceptible b) Regional geology differences
c) Soil covers much of the east d) Distances are shorter e) All of the above
- Probability is a valuable tool because it helps us avoid the over-interpretation of
a) circular reasoning b) selective memory
c) coincidence d) argument by authority e) All of the above.
- If an earthquake lasts about 30 seconds and the length of the fault that ruptured is about 90 km, what is the speed at which the rupture propagated?
a) 27 km/second b) 3 km/second c) 2.7 km/second
d) 9 km/second e) 30 km/second
- Earth's mantle is believed to be solid because
a) Surface waves do not pass through the mantle
b) Surface waves pass through the mantle
c) P-waves do not pass through the mantle
d) S waves travel through the mantle e) Trick question, Earth's mantle is liquid.
- P-wave paths through the mantle are curved upward because
a) The temperature increases with depth b) The P-wave velocity increases with depth
c) The P-wave velocity decreases with depth c) The mantle is solid
e) All of the above.
- Oceanic crust is composed of
a) most of the naturally occurring elements b) material extracted from the mantle
c) principally, eight common elements d) many old (billions of years) rocks
e) All of the above
- The fault parameter measured as a compass direction is
a) dip b) strike c) slip
d) hanging wall e) foot wall f) All of the above
Use the letters such as A, B, C, etc. to identify the seismic waves. Be sure to label each wave on each of the three seismograms (some responses may have multiple entries).
- The P-wave
- The S-Wave
- The Rayleigh Wave
- The Love Wave
- The Tsunami wave
- Surface Waves
- Body Waves
- The earthquake is located in the
a) north-south direction b) east-west direction
c) northwest-southeast direction d) northeast-southwest direction
d) directly below the seismometer
- Assuming that (1/Vp - 1/Vs) is approximately 1/8, estimate the distance from the seismometer to the earthquake (Vp is the P velocity, Vs is the S velocity).
a) 10 / 8 km b) 20 / 8 km
c) 10 x 8 km d) 20 x 8 km
d) 30 / 8 km
Match the flawed argument with the appropriate "problem" thinking
a) it happens after, so it must be true b) over-reliance on authority
c) carrying an argument to an extreme d) selective memory e) ad hominem
f) Since we don't understand it must have a supernatural cause. g) ad ignorantiam
- My colleague is a well-known biblical fundamentalist so there is no need to take him serious in a discussion of evolution.
- Since scientists can't prove that UFO's are visiting Earth it must be happening.
- If I eat an ice-cream today I may really like it which will lead me to eat more, eventually eating so much that I put on weight and shorten my life.
- I always ski better when I wear my lucky hat.
- A well-known physicist testifies that zinc tablets provide immediate relief from cold symptoms.
- A cancer patient undergoes long lasting, spontaneous remission - it must be a miracle.
- You think of a friend you haven't talked to in a while and they call you later that week.
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Prepared by: Charles J. Ammon