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 h = 200,000 m, h max = 5000 m h/ = 1/40 h/ < 1/20 = shallow water wave

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

4. Tsunami warning: simple c = √(gh) – g ~10 m/s – h average ~ 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.