McGill University
Faculty of Science
Department of Earth and Planetary Sciences
Earthquakes & Earth Structure -- EPSC 330
Final Examination -- Take Home
Examiner: Professor Olivia Jensen
Assoc. Examiner: Professor Jeanne Paquette
Assigned: Monday, April 14, 2014
due:
April 17, 2014 at 5:00PM
Instructions: This final take-home examination is due April 17, by 5:00PM. I need some time to
grade the exams. Hand it in to Angela in the Departmental office. You may, exceptionally, appeal for
another window of time if you cannot follow this schedule.
The examination comprises 4 pages and 15 questions (total). Reference materials can be found in the
Presentations directory of the course website.
You are free to work together in groups and to use whatever reference materials you may choose. I
require that each examinee hand in a separate and individual examination paper for grading. You are
free to take whatever tack you choose, mathematical, descriptive, argumentative, opinionated,
whatever, in response to any question. I shall not prefer any particular approach in grading.
This paper comprises 15 questions: 14 are yours and 1 is mine as your responsible professor. You may
answer your own question. As there is no monitoring of your approach to completing this examination,
you are free to consult with the author of any particular question. Should you choose to do so,
however, I ask that you reference your consultation as a personal communication.
Please try to limit your response to each question to about ½ page in a standard examination booklet.
Examination booklets are available from the Departmental office.
This exam contributes 40% toward your final grade. Each of the 15 questions/answers contributes
equally to the grade on this exam. Keep your answers short!
1. Question 1 (Olivia Jensen)
Among the myriad seismic wave types are the P-wave, the S-wave, the PP, the pP, the PP, the PcP, the
PcS, the ScS, the PKiKP, etc.. etc. (all body waves travelling through the volume of the Earth) and the
Rayleigh, the Love, the Stonely, the tsunami, etc. (all surface or boundary waves travelling along some
2-dimensional surface within or on the Earth). All such wavetypes conspire through constructive
interference to produce the complex standing wave phenomenon of seismic free oscillations, the socalled mechanical free modes of the Earth. One of these free modes, normally designated 0S2 is the
gravest (i.e., the lowest frequency) mode of seismic motion on the Earth and so might be regarded as
the proper low-frequency limit of seismology. This mode is sometimes called the "football mode" as it
is like the fundamental oscillation of a hard-kicked soccer ball as it flies through the air. This mode has
a period of about 54 minutes. This mode like every other true seismic mode except for the undertone
Slichter mode, often designated -nS1, and the family of so-called "breathing modes", normally
designated nS0, is comprised of a constructive interference of both dilatational (P-type) and shear (Stype) waves. While such interference is, perhaps, difficult to conceptualize except through
mathematical-physical description, that of the fundamental (gravest) "breathing mode", 0S0, is not. It
is the simplest, purely dilatational mode (i.e., no S-type waves are involved) of Earth oscillation.
Using simple diagrams, describe the internal interference pattern of P-type travelling waves
reverberating within the body of the Earth that conspire to form the fundamental dilatational 0S0 mode
as a standing wave. Note that everywhere on the surface, the amplitude of the wave is “in phase”.
Given that the travel-time of the purely dilational PKP wave through the centre on the Earth to the
antipode (the point exactly on the opposite side) of the Earth is about 20.2 minutes, argue for the
natural period of the 0S0 mode. Show diagrams of the standing wave patterns. Note that in order for
the standing wave form the "breathing mode", the phase of the wave must be coherent over the entire
surface.
2. Victor Abravanel: "Describe both active mass damping and the seismic invisibility cloak. Give
a similarity and difference in the way each advanced technique provides earthquake resistance
to buildings."
3. Bosuk Kim: “Briefly describe the Van method and natural time analysis which was later
modified to enable the narrowing of the time window of earthquake prediction.”
4. Aidan Ditchburn-Trout: "How do seismic waves affect pore water pressure, and how does this
cause a landslide to occur?"
5. Isabel Fendley & Jyotsana Singh: Name at least three ways scientists study earthquakes that
occurred before seismometers were invented, referring specifically to features used to study the
1811-12 New Madrid earthquakes.
6. Nicholas Busque: "Of the approaches mentioned in my presentation for earthquake prevention
in large-scaled buildings, which is your preferred method? Justify your answer, and explain
what conditions would satisfy you design choice."
7. Daniel Hardwick: What is a potential cause of non-volcanic tremor, and how is it different
from volcanic tremor? How does non-volcanic tremor relate to low frequency earthquakes?
8. Anne-Sophie Berg & Annelise Miska: “How do you distinguish moonquakes from
anthropogenic and meteorite impacts on a seismogram?”
9. Sissi (Shi Liu): Who invented the seismoscope, and when? What is the difference between the
seismoscope and the seismometer?
10. Konrad Chrzastowski: What were the pieces of evidence that allowed us to date the January
26, 1700 mega thrust earthquake that occurred on the Cascadia Subduction zone.
11. Edward Shin: Have you ever experienced an earthquake or an earthquake related hazard
yourself? Describe the earthquake in detail (location, magnitude, intensity, cause, damage,
reaction, duration, etc). If you don't have a personal experience, then discuss the most
devastating earthquake that have occurred in your country of origin. How did people respond to
the earthquake and its related damage?
12. Vladyslav Rayda: During shale gas extraction operations two different types of wells are
commonly used; one is the fracking well and other is the wastewater well. Which of those two
has a higher potential of nucleating a greater magnitude earthquake and give two reasons why.
13. Dylan Haber: Explain the Broken Window Fallacy and how it relates to economic growth in
the wake of an earthquake.
14. Kelian Dascher-Cousineau: By various astronometric means, we have well determined the
moment of inertia of the rotating Earth about its rotation axis: I = 0.3308 Mearth req2 and its
siderial rotation period, T = 23h 53m 4.091s.
What if the Earth were hollow? If the Earth were a hollow sphere with all of its mass evenly
distributed in a thin layer over its surface and rotating with its current angular momentum,
what would the length of its siderial day (i.e., 1 rotation relative to the inertial fixed stars) be?
What if the Earth were flat? If the Earth's mass were evenly distributed over a disc with Earth's
radius, what would the length of day be.
15. Matthew Tarling: An estimation of earthquake depth can be obtained using the arrival time
difference of certain depth phases of the seismic signal. In particular, the P and pP waves can be
used to obtain a rough estimate of hypocenter depth. At large surface distances between the
epicenter and the receiver, the P and pP waves travel on nearly the same path :
where Tp and TpP are the wave arrival times, h is the earthquake depth and v is the average P-wave
velocity between the focus and the surface.
Use the CMB record (figure following) of the Mw ~ 8.3 Sea of Oktosh event to estimate its depth. The
pP phase is quite clear in this seismogram. Note that this record is time-compressed so that one full
sweep of the seismogram equals 30 minutes (i.e. 180 seconds between vertical lines).
Compare your results to the reported depth. Briefly explain any differences.