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I. What is a tsunami

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I. What is a tsunami

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    2. I. What is a tsunami? 1. Japanese term derived from the characters a. “tsu” = harbor b. “nami”= wave 2. Also called “seismic sea waves” 3. A series of traveling ocean waves of extremely long length associated primarily with submarine earthquakes.

    3. What is a tsunami? 4. Tsunamis can also be caused by the following: a. volcanic eruptions, caldera collapse, volcanic landslides b. submarine landslides c. asteroid/comet marine impacts d. meteorological effects

    4. II. What causes waves? 1. Waves are created by releases of energy (disturbances) including: a. Wind b. Movement of fluids of different densities c. Mass movement into the ocean (splash waves) d. Underwater sea floor movement (tsunami) e. Pull of the Moon and Sun (tides) f. Human activities

    5. 2. Wave characteristics & terminology

    6. 3. Fully developed Sea a. Factors that increase wave height: 1) Increasing wind speed 2) Increasing duration (time) of wind 3) Increasing fetch (distance) b. A fully developed sea is the maximum height of waves produced by conditions of wind speed, duration, and fetch

    7. 4. Largest wind-generated waves authentically recorded a. In 1935, the vessel USS Ramapo experienced large waves while crossing the Pacific Ocean. b. Wave height was measured at 34 meters (112 feet)

    8. 5. Waves undergo physical changes in the surf zone

    9. III. Why does a tsunami happen?

    12. IV. Tsunami characteristics 1. Affect entire water column, so carry more energy than surface waves. 2. Cross ocean basins with little loss of energy. 3. Can travel at speeds over 700 kilometers (435 miles) per hour 4. Small wave height in the open ocean, since wavelengths are hundreds of kilometres long: so pass beneath ships unnoticed 5. Build up to extreme heights in shallow coastal areas.. Run-up heights of tens to hundred metres. 6. Transmit destruction to locations remote from source.

    13. 7. Coastal effects of tsunami a. If trough arrives first, appear as a strong withdrawal of water (similar to an extreme and suddenly-occurring low tide) b. If crest arrives first, appear as a strong surge of water that can raise sea level many meters and flood inland areas c. More than one wave (wave train) so tsunamis often occur as a series of surges and withdrawals

    14. 8. Tsunamis: velocity, wavelength and depth a. As the wave approaches the shoreline, it slows and as it slows the rear portion of the wave crashes into the front and the height of the wave grows tremendously.

    15. V. Notable tsunamis in history and prehistory

    16. 2. The Pacific a. Over 1200 tsunamis reported in Pacific since 47 BC b. Main sources: 1) Alaska 2) Kamchatka 3) southern Chile c. Highest risk areas 1) Northern California 2) Hawaii 3) Chile, Peru d. 500,000 estimated deaths in last 2000 years

    17. 3. The Mediterranean a. High risk areas 1) Eastern Mediterranean 2) Straits of Messina 3) off southern Portugal b. Italy ~ 67 tsunamis in last 2000 years c.1908 Messina (Italy) quake 1) Tsunami killed 8,000

    18. 4. The Atlantic a. Tsunamis rare - not unknown b. LISBON quake 1755 1) 15 m high tsunami 2) Damaging 7m wave recorded in Caribbean c. Caribbean: frequent tsunamis

    19. 5. Major tsunami threat in the Atlantic Basin a. Up to 500 km3 of west flank detached and unstable b. Dropped 4 meters during eruption in 1949 c. Future collapse will be catastrophic d. Timing: future eruption. Frequency – 20 to 200 y e. Major tsunami threat to Atlantic rim

    20. The resulting tsunami?

    21. VI. Tsunami Vocabulary 1. Local Tsunami- A local or near-field tsunami has a very short travel time (30 minutes or less) 2. Regional Tsunami- A regional or mid-field tsunami has travel times of between 30 minutes and two hours 3. Teletsunami- A distant source or far-field tsunami. Travel time is greater than two hours 4. Arrival Time- Time of arrival of the first wave 5. ETA- Estimated time of arrival of wave after earthquake strikes

    22. Tsunami Vocabulary (cont) 6. Inundation- The depth to which a particular location is covered by water. 7. Inundation Area- The area that is flooded with water 8. Horizontal Inundation Distance- The distance a tsunami wave travels onto the shore. 9. Runup- The maximum height of the water that comes up onshore. 10. Seiche- A standing wave oscillating in a partially or fully enclosed body of water 11. Marigraph- An instrument which records wave height

    23. 12. Bore a. Traveling wave with an abrupt vertical front (think wall of water) b. Formed as it approaches shore or when it enters a river channel ( it may travel further than the original inundation) c. Normal associated with a “tidal bore”

    24. Tsunami Vocabulary (cont) 13. Period -The length of time between two successive peaks or troughs. Tsunami periods range from five to sixty minutes 14. NOAA- National Oceanic and Atmospheric Administration 15. NWS- National Weather Service

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