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Tsunami! Understanding the Generation, Propagation, and Hazards of Tsunamis

Larry Braile, braile@purdue.edu , web.ics.purdue.edu/~braile Sheryl Braile NSTA, Boston, 2008. Tsunami! Understanding the Generation, Propagation, and Hazards of Tsunamis. (Despite the popularity of this image, tsunami waves do not normally look like this.).

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Tsunami! Understanding the Generation, Propagation, and Hazards of Tsunamis

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  1. Larry Braile,braile@purdue.edu, web.ics.purdue.edu/~braile Sheryl Braile NSTA, Boston, 2008 Tsunami! Understanding the Generation, Propagation, and Hazards of Tsunamis (Despite the popularity of this image, tsunami waves do not normally look like this.) This PowerPoint Presentation (last modified March 14, 2008): http://web.ics.purdue.edu/~braile/edumod/tsunami/Tsunami!.ppt

  2. Tsunamis can be generated by: • Large Earthquakes (megathrust events such as Sumatra, Dec. 26, 2004) • Underwater or near-surface volcanic eruptions (Krakatoa, 1883) • Comet or asteroid impacts (evidence for tsunami deposits from the Chicxulub impact 65 mya) • Large landslides that extend into water (Lituya Bay, AK, 1958) • Large undersea landslides (evidence for prehistoric undersea landslides in Hawaii and off the east coast of North America)

  3. Schematic plate tectonic setting for tsunami generation TRENCH NOAA Commonly, in mega-thrust earthquakes, a very large area of the ocean floor is uplifted

  4. Earthquake generation of tsunami (note: tsunami wave in the animation should be asymmetrical with a first peak traveling to the right and a first trough traveling to the left) Animation http://ffden-2.phys.uaf.edu/645fall2003_web.dir/elena_suleimani/generation_small.mov http://web.ics.purdue.edu/~braile/edumod/tsunami/TsunamiFiles.htm

  5. Blind Thrust Fault Earthquake Rupture Animation (Northridge, 1994) Brad Aagaard, USGS http://pasadena.wr.usgs.gov/office/baagaard/research/animations/animations.html The fault rupture will be visible in the animation. Displacements (magnified 3000 times) will be visible by the movement of the mesh from the model. The amplitude of motions and seismic waves is color coded according to ground velocity. Note the rupture along the fault over time from the deepest extent of the fault. http://web.ics.purdue.edu/~braile/new/AagaardBlindThrustAnimation.ppt Exploring Planet Earth

  6. Blind Thrust Fault Earthquake Rupture Animation – Brad Aagaard, USGS http://pasadena.wr.usgs.gov/office/baagaard/research/animations/animations.html The fault rupture will be visible in the animation. Displacements (magnified 3000 times) will be visible by the movement of the mesh from the model. The amplitude of seismic waves is color coded according to ground velocity.

  7. Earthquake Rupture http://pasadena.wr.usgs.gov/office/baagaard/research/animations/animations.html

  8. Worldwide earthquakes per year (from USGS):

  9. Worldwide earthquakes per year: Frequency-magnitude relationship suggests that magnitude 9+ events will occur about once per decade, statistically; since 1900, the actual number is ~once per 20 years.

  10. Tsunami Statistics Tsunami Statistics (NOAA): http://wcatwc.arh.noaa.gov/tsustats.pdf (Dec. 26, 2004 tsunami resulted in over 200,000 deaths) Tsunami Statistics (NOAA): http://wcatwc.arh.noaa.gov/tsustats.pdf

  11. Tsunami wave propagation characteristics – note that as water depth becomes smaller, waves slow down, become shorter wavelength, and have larger amplitude. NOAA When the water is 10 m deep, what is the separation of the waves in minutes?

  12. Water waves animation Direction of propagation Animation courtesy of Dr. Dan Russell, Kettering University http://www.gmi.edu/~drussell/demos.html

  13. Tsunami velocity and amplitude equations (These are plane layer [flat ocean bottom] equations) • Wave velocity controlled by water depth: v = (g x d)1/2 where v is velocity, d is water depth and g is the acceleration of gravity = 9.8 m/s2; so, velocity decreases in shallower water. • Wave height (amplitude) increases (conservation of energy) in shallow water: AS = AD x (VD/VS)1/2 where AS = amplitude in shallow water, AD = amplitude in deep water, VS = velocity in shallow water, and VD = velocity in deep water.

  14. Wave Heights – Satellite observation versus calculated model – open ocean, deep water ~1600 km; ~2.2 hours of waves at 750 km/hr Geist, Titov and Synolakis, Tsunami: Wave of Change, Scientific American, January, 2006.

  15. Tsunami Wave Tank • 1. “SnapLock Select” plastic underbed storage box • 118 x 51 x 13 cm (45” x 21” 5”) from Walmart, K-Mart, etc. • (or Sterilite #1996), remove handles, fill holes with • silicon sealer. • 2. Plexiglass • 53 x 48 x 0.5 cm • (21” x 19” x 3/16”) • [could use • sand for “coastal • area” instead of • plexiglass]. • Two 30 cm plastic • rulers with clay • base, 30 cm apart. • Fill to 8 cm deep • with water.

  16. Tsunami Wave Tank

  17. Tsunami Wave Tank (close-up of ruler and plexiglass – note slope representing shallowing of water depth adjacent to coast)

  18. Tsunami Wave Tank – Video of Wave Tank Download Tank.mov from: http://web.ics.purdue.edu/~braile/edumod/tsunami/TsunamiFiles.htm

  19. Tsunami Wave Tank – Video of Waves Water Drop – Point source, circular spreading of energy: Download WaterDrop3.mov and WaterDrop4Measure.mov from: http://web.ics.purdue.edu/~braile/edumod/tsunami/TsunamiFiles.htm 1. What are the characteristics of the waves generated by the water drop? 2. Measure the velocity of the wave using a stopwatch (distance from center to side of tank in cm, divided by time in seconds). 3. Can you observe reflected waves. 4. Why do the waves eventually disappear?

  20. Tsunami Wave Tank – Video of Waves Line Source (plane wave) – No spreading of energy: Download PlaneWave1.mov from: http://web.ics.purdue.edu/~braile/edumod/tsunami/TsunamiFiles.htm 1. What are the characteristics of the waves generated by the line source? 2. Measure the velocity of the wave using a stopwatch (follow one wave crest from first ruler to the second – 30 cm divided by time). 3. What is the wave height? 4. What is the wave length? 5. Do the waves get smaller with distance of propagation? 6. What type of water wave in the ocean is similar to these waves?

  21. Ocean Waves

  22. Tsunami Wave Tank – Video of Waves Tsunami – Line source and entire water column disturbed: Download Tsunami2.mov from: http://web.ics.purdue.edu/~braile/edumod/tsunami/TsunamiFiles.htm • What are the characteristics • of the waves generated by the • tsunami source? • 2. Measure the velocity of the • wave using single frame advance • (follow one wave crest from first • ruler to the second – 30 cm • divided by time). • 3. What is the wave height? • 4. What is the wave length? • 5. What happens to the wave • as it propagates into shallow • water?

  23. Tsunami Wave Tank – Video of Waves Tsunami – Line source and entire water column disturbed: Download Tsunami4Measure.mov from: http://web.ics.purdue.edu/~braile/edumod/tsunami/TsunamiFiles.htm (Use pause and single frame advance to observe wave characteristics) ~5.8 s ~6.2 s  Note Long Wavelength  Note Wave Cresting 

  24. Tsunami Wave Tank Materials Wave generation sources; drop into water or oscillate up and down on water surface to create waves: Golf ball, plastic golf ball (or table tennis ball), eye dropper, clay, wood, styrofoam strips 48 x 10 x 2.5 cm (19” x 3.75” x 1”)

  25. 26 Dec. 2004 Tsunami max. wave height and arrival time Geist, Titov and Synolakis, Tsunami: Wave of Change, Scientific American, January, 2006.

  26. Seismic Eruption software: http://www.geol.binghamton.edu/faculty/jones/ Indonesia area historical earthquakes files, download from: http://web.ics.purdue.edu/~braile/edumod/tsunami/TsunamiFiles.htm

  27. Seismic Eruption software: http://www.geol.binghamton.edu/faculty/jones/ Sumatra earthquake and aftershocks files, download from: http://web.ics.purdue.edu/~braile/edumod/tsunami/TsunamiFiles.htm

  28. Tsunami simulation (Note focusing of energy to west and east of the earthquake rupture area) http://staff.aist.go.jp/kenji.satake/animation.gif

  29. Chedi Resort, Phuket, Thailand, wave height ~4+ m (?, from estimates of water level from beach umbrellas on grassy area above the beach)

  30. Banda Aceh, Sumatra, before tsunami http://geo-world.org/tsunami/

  31. Banda Aceh, Sumatra, after tsunami Also: http://www.digitalglobe.com/

  32. Tsunami Resources Tsunami Teacher Resource Kit (17 MB pdf) from ITIC (International Tsunami Information Centre) http://www.tsunamiwave.info/

  33. Tsunamis – Wall of Water activities (University of Texas, Institute of Geophysics) http://www.ig.utexas.edu/outreach/cataclysms/modules.htm

  34. IRIS Posters: http://www.iris.edu/about/publications.htm#p

  35. Larry Braile,braile@purdue.edu, web.ics.purdue.edu/~braile Sheryl Braile NSTA, Boston, 2008 Tsunami! Understanding the Generation, Propagation, and Hazards of Tsunamis (Despite the popularity of this image, tsunami waves do not normally look like this.) This PowerPoint Presentation (last modified March 14, 2008): http://web.ics.purdue.edu/~braile/edumod/tsunami/Tsunami!.ppt

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