Geography and Oceanography - Chapter 6 docx
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Earthquakes, Tsunamis,
and the Oregon Coast
When will the next Megaquake occur?
Why are tsunamis so destructive?
How much of the coast is affected?
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Earthquake Zones
Plate boundaries
Spreading ridges
Collisions
Sliding
Earthquakes require
strong, brittle rock
Accumulated strain
(“elastic”)
shallow
deep
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Tsunami
Sudden shifting of the ocean floor due to
earthquakes, volcanic eruptions, and
submarine slumping.
open ocean: short heights, long wavelengths
(>100 km), and long periods 400-500 mph!!!
shallow water: their length shortens and their
height increases dramatically.
These are NOT tidal waves
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Tsunami Animation
/>5
Sumatra 2004, >275,000 Dead!
Sumatra 2004, >275,000 Dead!
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Before
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After
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Courtesy of Mate 3
rd
Class Tyler
J. Clements/U.S. Navy
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Japanese 8.9 Earthquake and Tsunami
(March 11, 2011) ~18,000 dead
video: />13
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Tsunami Sea floor thrust fault
2004 Sumatra M9.3, 1200km fault, 15m slip
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Mega-Slumps can trigger tsunami
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