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Tsunamis GEOL 4093 Risk Assessment
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Tsunamis Also known as “seismic sea waves” Generating force is not wind, but movement of the sea floor, volcano, landslide, etc. Travel rapidly over great distances
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Tsunami Characteristics Extremely long wavelengths (100-200 km) Long periods (10-20 minutes) Low wave heights (1-2 meters) Shallow water waves
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As the tsunami wave gets closer to shore, its speed decreases but its wave height greatly increases.
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Tsunami in Hilo, Hawaii from 1946 Aleutian Islands Earthquake
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1960 Chile Earthquake Magnitude 9.5 Earthquake deaths in the thousands Tsunami deaths: –Hawaii—61 –Japan—120 –Phillipines—20
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Tsunami damage from 1960 Chilean earthquake
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Computer simulation of tsunami caused by 1960 Chilean Earthquake. Time: 0:00.
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Time: 1:40 hrs
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Time 3:20 hrs
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Time 5:00 hrs
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Time 10:00 hrs
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Time 15:00 hrs
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Time 20:00 hrs
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Time 25:00 hrs
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A wave front rushes up the Wailuku River in Hilo, Hawaii, during the tsunami of 1 April 1946.
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Tsunami in Hilo Hawaii, on April 1, 1946
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Tsunami in Hilo, Hawaii from Aleutian Islands earthquake
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Scoth Cap Lighthouse was destroyed by tsunami from Aleutian Islands earthquake of April 1, 1946. The lighthouse stood 30 feet above sea level
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The next three slides show the sequential arrival of a tsunami at Laie Point, Oahu Island, Hawaiian Islands. The 8.3 magnitude 8.3 earthquake of March 9, 1957 in Alaska generated a tsunami that struck the beachfront of Hawaii, about 3,600 km from the generating area.
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Japan, July 1993. The largest tsunami to strike Japan in recent times. Waves washed 29 meters (97 feet) above sea level; 120 people died.
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In addition to the Pacific- wide early warning system (A) there are also regional warning systems (B-F), which warn residents about 10 minutes or 100-750 km from source. THRUST: A local warning system to warn within 100 km from the source.
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Not all tsunamis are caused by earthquakes. Here a landslide at the far end of this Alaska bay destroyed a forest in the foreground.
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Krakatau, Indonesia, famous for its devastating 1883 eruption, one of the largest in history. Tsunamis reached heights of 40 m killed 36,000 people on the low shores of Java and Sumatra.
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Tsunami inundation maps show areas of potential flooding.
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Seiches Periodic standing-wave oscillation of water surface Occur in enclosed basins Travels back and forth at regular intervals Can be caused by winds, currents, pressure, earthquakes, landslides
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Water sloshes up and down around a central node
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The 1989 Loma Prieta earthquake was near enough to Monterey Bay to initiate seiche waves in the bay.
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