1. AST 2005 1

2. 2 Tsunami Dan Kelley Dept. Oceanography Dalhousie University Dan.Kelley@Dal.Ca

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4. 4 1. Background

5. AST 2005 5 harbour ("tsu", 津 ) wave ("nami", 波 or 浪 )

6. AST 2005 6 Background Harbour ("tsu", 津 ) wave ("nami", 波 or 浪 ) so named since seen in harbours, not at sea. See: WikiPedia(overview) See NOAA, USGS, etc. (research)

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9. 9 Students can easily find material on the 2004 event, and...... they would find that interesting, so...... class time could be directed otherwise... maybe on learning wave Physics :-)

10. AST 2005 10 2. Wave Physics

11. AST 2005 11 Shallow- versus deep-water waves [what does “shallow” mean?] Wave speeds depends on geometry [contrast shallow- and deep-water cases] Mathematics = a good thing (™ M. Stewart)

12. AST 2005 12 AST 2005 Shallow- & deep-water waves There are many implications of these flow patterns

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14. AST 2005 14 “Shallow-water” wave theory applies if wavelength greatly exceeds water depth, λ >>H

15. AST 2005 15 Shallow-water wave speed... mathematical fun

16. AST 2005 16 A traveling wave has

17. AST 2005 17 Momentum Equation Water acceleration Accel. due to gravity Tilt of ocean surface

18. AST 2005 18 Water-conservation Equation Heaving velocity of ocean surface Water depth Convergence of water

19. AST 2005 19 If then Thus wave speed is Wave equation

20. AST 2005 20 Summarizing the above, if then wave speed is get H from bathymetric chart Use C to predict wave arrival time

21. AST 2005 21 3. “Shallow” shallow-water case

22. AST 2005 22 Wave refraction into shallow water

23. AST 2005 23 Trust me, I could go on with the beach case... AST2006 perhaps?

24. AST 2005 24 4. “Deep” shallow-water case

25. AST 2005 25 Seismic Forcing has 500 km

26. AST 2005 26 Forcing region

27. AST 2005 27 1300km Forcing region

28. AST 2005 28 2h 8h 2h

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30. AST 2005 30 5. Student Exercise

31. AST 2005 31 Ray-path & wave-front calculation Ideas, and thus exercise, has applications to Electricity & Magnetism, etc.

32. AST 2005 32 Wave front from distributed source (cf. antenna theory)

33. AST 2005 33 Refracting wave front with varying water depth

34. AST 2005 34 Diagram by Ramzi Mirshak, Dalhousie PhD candidate Assign each student a dot. Group results yield wave fronts. (Richardson’s scheme.)

35. AST 2005 35 AST 2005 Lewis Fry Richardson 1881- 1953 Working alone, took several months to make a terribly inaccurate 6-hour forecast of Munich weather Idea for numerical weather prediction: roomful of people doing calculations (“cpu”) and handing back and forth slips of paper (“bus”). "Big whorls have little whorls that feed on their velocity, and little whorls have smaller whorls and so on to viscosity."

36. AST 2005 36 6. Tsunami Impact

37. AST 2005 37 Local Impact

38. AST 2005 38 AST 2005 Newfoundland 1929 Laurentian slope earthquake, magnitude 7.2 Tsunami of 7m @ southern Nfld 28 deaths

39. AST 2005 39 AST 2005 History c. 1600BC Tsunami devastated Crete [Atlantis?] 1883 Krakatoa volcanic explosion -- 40m tsunami 1964 (Good Friday) -- 6m wave, killed 121 people in Alaska/BC and 11 in California 2004 Indian Ocean -- killed 270,000 people

40. AST 2005 40 AST 2005 Conclusions Use Tsunami to motive a study of wave physics Wave physics is an EASY and FUN way to learn calculus... why wait until university to see DEs... why wait to see partial derivatives?