890 likes | 1.12k Views
Tsunami. Tsunami. Very fast wave with a HUGE wavelength , triggered by a disturbance. Velocity. Landslides Volcanic eruptions Meteor impacts Earthquakes. 2004 Sumatra. 2004 Sumatra. Lituya Bay, Alaska. 1,720 feet. Shallow- vs. Deep-water waves. Shallow- vs. Deep-water waves. λ.
E N D
Tsunami Very fast wave with a HUGEwavelength,triggered by a disturbance Velocity
Landslides • Volcanic eruptions • Meteor impacts • Earthquakes
Shallow- vs. Deep-water waves λ λ/2 Deep
Shallow- vs. Deep-water waves Shallow
Example • D = 3,800 m (average depth)
Wind Waves vs. Tsunamis Wind Generated Waves • 5-20 seconds period • 300-600 ft wave length • 10 kph speed Tsunami Waves • 10 min-2 hr period • Wave length HUGE (can be > 100 km) • 700 kph speed
E proportional to H2 × λ Height . . . 500 × greater!
Attenuation!! High frequency: treble Low frequency: bass
Velocity • Energy proportional to A2 × vLittle energy lost, soA2 × v ≈ constant • v decreases, A increases Amplitude
The Great Sumatra Tsunami of 2004 • MW = 9.3 • 275,000 dead • Waves up to 100 ft
Banda Aceh:June 23rd 2004 DigitalGlobe
Banda Aceh: December 28th 2004 DigitalGlobe
Gleebrook Village:June 23rd 2004 DigitalGlobe
Gleebrook Village: December 28th 2004 DigitalGlobe
Tsunami damage from: • Force of water (in & out) • Force of debris • Flooding (water damage) • Flooding (crop damage)
What is it like to experience a tsunami? • May be preceded by drop in water level • Several waves, separated by5 – 300 minutes • First is rarely largest Hilo, Hawaii Marigram
The Great ChileTsunami of 1960 • MW = 9.5 • Crossed ocean • Waves up to ≈ 20 ft
> 10,000 miles The Great ChileTsunami of 1960 Onagawa Japan
Onagawa, Japan, 1960 4:40 a.m.
Onagawa, Japan, 1960 4:45 a.m.
Onagawa, Japan, 1960 4:50 a.m.
Onagawa, Japan, 1960 7:30 a.m.
Tsunami produced by landslides, eruptions, impacts • Disturbance at surface λ ≈ size of disturbance • λ ≈ several km much SMALLER than earthquake tsunami • Attenuates faster • Causes local damage only
1842-2006: 3532+ deaths 1842-2006: 579 deaths
1918 Puerto Rico Tsunami Michael Count
1918 Puerto Rico Tsunami Michael Count