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Lecture

EARTHSC 2GG3 Lecture Notes - Burma Plate, Wind Wave, Plate Tectonics


Department
Earth Sciences
Course Code
EARTHSC 2GG3
Professor
Sergei Basik

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Tsunami
Tsunami(seismic sea wave) : an abnormally long wavelength wave produced by sudden
displacement of water
Near Field Tsunami: tsunami that strikes areas adjacent to its point of origin
Far Field Tsunami: tsunami that strikes areas distant from its point of origin
(ex. Indonesia tsunami)
(usually bigger and more damaging that near field)
Tsunami Wave
Long wavelengths (ex. 400 km long with amp of 50 cm
Velocity dependent of water depth
The wave is so big that there is frictional interaction with the ocean bottom
Eave slows down in shallower water
Wave increases its height as the water become more shallow near the coast
As wave gets closer to shore (shallow) slows down increases in height, wall of water
Velocity of Tsunami
C= sq rt (gD)
C velocity in metres per second
G - gravitational acceleration (9.8)
D Depth in meters
Depends on water depth and gravity
Near shore tsunamis are much slower (112 km/h) less velocity
Run-up Height & Run-out Distance
Storm Surge not as forceful
Tsunami forces of waves pushed up making it run up further inland (run-up height of 30-60 m even
hundreds of metres)
Tsunami Hazards
Lack of warning: difficult to disseminate information btw and within countries (which authorities to
call?)
Multiple Waves : time btw waves typically more than 30 min; 2nd or 3rd waves often worse than first
Contaminated water leading to disease
Subduction-Zone Earthquake and Tsunami Creation
Steps: 1) ocean plate subducts to continental plate 2) bulge of displaced water 3) bulge releases and
waves from this release roar to neares coastline
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