Download McGill University Faculty of Science Department of Earth and

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: Friday, April 22, 2016
due: April 25, 2016 at 5:00PM
Instructions: This final take-home examination is due April 25, 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 3 pages and 12 questions (total). Reference materials can be found in the
Presentations directory.
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 12 questions: 11 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 12 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. Meryem Berrada: "In modelling solar oscillations, what assumptions on the condition and
processes of the Sun do we make?"
3. Olivia Dagnaud: "Discuss earthquake distribution in India. How is intraplate seismicity
induced by the Indo-Asian continental collision?"
4. Robert Bourque: "What are some factors that influence the irregularities in the timing of faultslip sequences?"
5. Paige Magrogan: “How did the practice of earthquake archaeology change in response to the
1995 Kobe earthquake, and again after the 2011 earthquake and tsunami? What are some of the
particular strengths of earthquake archaeology in Japan compared to the Mediterranean?”
6. Thurstyn Parhar: “How can we use neutron stars to study gravitational waves? Both when
neutron stars cause gravitational waves, and when they are used to detect them.”
7. Alexis Beaupré Laperrière: “What factors, both geological and societal, can influence the
severity of damage induced by large magnitude earthquakes ?”
8. Mitchell May: “Discuss the geologic setting that gave rise to the Tohoku tsunami. How do fault
mechanics influence the resulting tsunami properties? Do you suppose a crest leading tsunami,
such as in the Tohoku event, is characteristic of subduction zone fault ruptures?”
9. Catherine Ross: “Draw and label a schematic diagram of the Cascade Subduction Zone with
the locked zone, ETS region, and where aseismic creep occurs. What is the difference between
their signals? “
10. Alexander Martell: "Describe Lamontagne's conclusions about the causes of the unusual
seismicity in the Charlevoix Seismic Zone."
11. Josiane Ostiguy: “What physical phenomena can be used to study geomagnetic variations
before and during earthquakes? Give a brief explanation of each effect and their connection to
earthquakes.”
12. Taylor Peacock: “If you lived in the Pacific Northwest how would you prepare yourself for a
major Cascadia Subduction Zone event?”