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Tsunamis and Tsunami Detection Systems

Tsunamis and Tsunami Detection Systems. December 1, 2010 Physical Oceanography Presentation Jeana Drake. What is a tsunami?. Shallow water wave Long wavelength ~200 km Small amplitude in open ocean ~30 cm Caused by earthquakes, landslides, volcanic eruptions, meteor impacts. l. h.

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Tsunamis and Tsunami Detection Systems

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  1. Tsunamis and Tsunami Detection Systems December 1, 2010 Physical Oceanography Presentation Jeana Drake

  2. What is a tsunami? • Shallow water wave • Long wavelength • ~200 km • Small amplitude in open ocean • ~30 cm • Caused by earthquakes, landslides, volcanic eruptions, meteor impacts l h • = 200,000 m, hmax = 5000 m • h/l = 1/40 • h/l < 1/20 = shallow water wave

  3. Why are tsunamis a problem? • Shallower depths near coasts force a decrease in l • That water has to go somewhere • Increase amplitude • E = (1/2)rga2 • r = density • g = gravity • a = amplitude

  4. Tsunami warning: simple • c = √(gh) • g ~10 m/s • haverage ~ 4000 m • c ~ 200 m/s • Portugal to Cuba (1755) • ~7000 km • ~9.5 hrs www.noaa.gov

  5. Tsunami warning: complicated • Regional • Seismic data from local earthquakes • Coastal tide gauges • DART buoys • International • DART • SOFAR channel www.noaa.gov

  6. Tsunami warning: New • GPS-based detection of horizontal & vertical movement of the seafloor near an epicenter. • GREAT • GITEWS • Quicker calculations • Fewer false alarms

  7. References • DART. www.noaa.gov • Falk et al. 2010. Near real-time GPS applications for tsunami early warning systems. Natural Hazards and Earth System Science 10: 181-190. • Knauss, J.A. 1997. Introduction to Physical Oceanography. Waveland Press, Inc. • Song, Y.T. 2007. Detecting tsunami genesis and scales directly from coastal GPS stations. Geophysical Research Letters: 34.

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