Geology 112 – Earthquakes
Name _____________________
Activity 15 - 1700 Pacific Northwest Earthquake and Orphan Tsunami
What is the due date? ____________________ (fill-in day, date and time -- see greensheet or
information at top of your learning group discussion for this activity in Canvas.
Objective: Learn about the scientific discovery of great earthquakes (M=9 or greater) along the
Cascadia subduction zone, and the potential for a future devastating event along northern
California, Oregon and Washington on the same scale as the 2004 Indian Ocean earthquake
and tsunami or 2011 Japan earthquake.
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Remember to answer the questions below and take notes
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Required learning group discussion instructions at the end of this worksheet
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First watch a 2 minute-long newscast about the expectation of a magnitude 9.0
earthquake along northern California, Oregon and Washington, followed by
a 50 minute-long program from the BBC, the Next Megaquake, divided into five 10
minute-long segments on YouTube. A transcript of the program can be access at
http://www.bbc.co.uk/sn/tvradio/programmes/horizon/megaquake_prog_summary.shtml if
you need it.
After the BBC show, view two segments of the NOVA program, Deadliest Earthquakes,
one 3 minutes-long and another 8 minutes-long, on the recent scientific studies on
understanding the frequency of great earthquakes along the Cascadia subduction zone,
using sediment samples from the deep-sea and measurements of tiny, nearly
imperceptible “slow-slip” earthquake that may foretell a great earthquake?
I. The Situation - Pacific Northwest Cascadia Subduction 9.0 Earthquake Expected at
Anytime
View http://youtu.be/X5eloPKhzAM (2 minutes) -- More than 10,000 people could die
when — not if — a monster earthquake and tsunami occur just off the Pacific Northwest
coast, researchers told Oregon legislators Thursday.
II. Watch The Next Megaquake (called Cascadian Megaquake 1 of 5 on YouTube):
Segment 1 – 10 minutes long at http://youtu.be/NP8cDXsvH8A
1. Where might a great earthquake strike the United States, close to California, and which
cities are at risk?
2. What tectonic process operates along the plate boundary beneath the coast of northern
California, Oregon and Washington?
3. Describe the deformation of the lithosphere along a subduction zone, ultimately leading
to a great earthquake?
4. How is a tsunami different than a wind-driven wave on the surface of the ocean?
5. How is the seismic activity along Cascadia subduction zone different from many other
subduction zones worldwide and how did scientists interpret this characteristic early on?
6. What intriguing evidence first caused scientists, like Brian Atwater, to challenge the
prevailing idea at the time aboput the potential for a great earthquake in this region?
Segment 2 – 10 minutes-long at http://youtu.be/LjDixpGsBf4
7. How did Atwater find the initial evidence of a great earthquake and what was the
evidence?
8. What is the evidence for a tsunami following the great earthquake?
9. Explain the Atwater’s hypothesis for a great earthquake based on the observations
described in the previous two questions?
10. How was a rough date provided for the hypothesized event?
11. What piece of evidence, recorded in Japan, was used to identify the year of the tsunami?
12. What was the date of the tsunami in Japan and how was this determined?
13. How many tsunamis hit Japan on that January day in 1700?
14. What was unique about the tsunami once it arrived along the shores of Japan?
15. What is the final piece of evidence that linked all of the previous observations, both in
Japan and along the coast of the Pacific Northwest, into a coherent theory?
16. What killed the trees in the ghost forest?
17. What data provided evidence for the simultaneous death of the trees?
18. What was the date, year and time of the Cascadia earthquake (along north America)?
19. What were the effects that followed this great earthquake?
Segment 3 – 10 minutes-long at http://youtu.be/3SofGBUfEyw
20. How does the length of fault rupture compare to the size of the earthquake?
How does the length of the fault rupture of the 2004 (M=9.3) Indian Ocean earthquake
compare to that estimated for the Cascadia earthquake in 1700?
21. Will there be another great Cascadia subduction zone earthquake in the future? Why or
Why not?
22. What key question remains largely unanswered about the damage to buildings in the
future Cascadia earthquake and why?
23. What type of buildings will definitely be at risk and may result in great damage and loss of
life?
Segment 4 – 10 minutes-long at http://youtu.be/axHrvAxroUI
24. How do geologists learn about frequency of earthquakes in the past?
25. When might the next great earthquake occur along the Cascadia subduction zone?
26. What can we do to limit the damage of the next great earthquake and loss of life?
27. How may the fault rupture begin and evolve over the duration of the earthquake?
28. Why is the tsunami predicted to have a devastating effect on the shores of the Pacific
Northwest and maybe somewhat less so in Hawaii, Japan and even southern California?
29. Why is the ground shaking forecasted to be severe at the coast along the Pacific
Northwest?
30. How is the state of Washington preparing for this eventual earthquake?
Segment 5 – 9 minutes-long at http://youtu.be/W-ANmIaVMUk
31. How should the public react if within a building when the strong ground shaking begins?
32. What is the major hazard to the public in outside areas and what should people do?
33. What will happen to the unreinforced masonry (URM) buildings?
34. How does the duration of shaking affect the structural integrity of the buildings?
35. How will the shaking affect buildings on higher ground, especially on sloping hillsides?
36. If the tsunami warning system is relatively ineffective along the coast of the Pacific
Northwest, what then should people on the coast do if the ground shakes violently?
37. What is the best way for people in coastal regions to prepare now, prior to the eventual
tsunami?
This is end of the MegaQuake program.
II. First segment of NOVA program “Deadliest Earthquakes” on the Cascadia megathrust
(Program website with written transcript at:
http://www.pbs.org/wgbh/nova/earth/deadliest-earthquakes.html)
Watch this segment on YouTube at http://youtu.be/I9LDXRcaWpw
Fast forward player to the 11:43 time mark to watch the last two minutes of this
segment (we will cover other segments of this program later in the course)
38. What type of data is Chris Goldfinger using to study the history of Cascadia megathrust
earthquakes and how are these data acquired, and over what period of time?
Move on to watch the first 8 minutes of the next segment of the program at
http://youtu.be/o4n3drwryg0
39. Describe the nature of the scientific analysis of the core samples being carried out by
Chris Goldfinger and what is he trying to identify?
40. What is the principal conclusion of this research and it’s implications for the probability of
great earthquakes along the Cascadia megathrust in the future?
41. What is Ken Creager attempting to measure and how?
42. How often do these silent earthquakes occur and how long do they last?
43. What is the hypothesis or question that Ken Creager is testing with his research?
44. What is the potential implication of this research?
Stop at the 8:00 minute mark of this segment
Required Learning Group Discussion Assignment (6 points)
• After completing this expedition, go to your learning group discussion and
then post two multiple-choice questions how scientists are studying the
earthquake and tsunami potential of the Cascadia subduction zone, and potential
damage, each with 5 potential answers (a, b, c, d, and e); do not highlight the
correct answers to your questions.
• Scoring on required posting will be based on the clarity (ability to communicate
in writing) and quality (scientific insight) of the posted questions and the listings
of potential answers.
• Ambiguous questions or answers, or error in writing quality, will receive point
deductions – be clear and precise.
• Do not repeat a question posted previously by another student in your learning
group, which will consist of 8-9 other students in the class.
• Students will then provide feedback on the clarity and quality of the questions
posted by the student immediately above their own posting in the learning group
discussion and then answer the questions.
• First student to post in a learning group receives an extra 48 hours, after
deadline, to answer the posting of the last student to post in the group by the
deadline.
• After your questions have been answered, provide feedback on the accuracy of
the answers and examine the work of your other learning group members to
compile a list of the top six questions covering the breadth of material in this
activity.