Briefly describe how tsunami are generated and include a ...

[abarnes]

Briefly describe how tsunami are generated and include a description of characteristics such as wavelength and wave speed.
 
  Do tsunami behave as shallow-water waves? Why or why not and how does this influence their movement in shallow versus deeper water? What would the shoreline look like when the trough of tsunami arrives?

Question 2

Using examples, explain how wave refraction is different from wave reflection.
 
  What will be an ideal response?

[Viet Thy]

Answer to Question 1

Tsunami are shallow-water waves generated by sudden changes in the topography of the ocean bottom caused by events such as underwater avalanches, turbidity currents, and fault motion. Tsunami have long wavelengths, typically exceeding 200 km (125 miles) and fast wave speeds (> 700 km or 435 miles/hr). In deeper water, tsunami can typically go unnoticed, but because they travel as shallow-water waves, as they approach shore, their speed decreases, but wave height can increase. As tsunami approach a shoreline, the water level typically decreases (the wave trough), followed by a series of surges and withdrawals of water that are widely separated in time.

Answer to Question 2

The slowing and bending of waves in shallow water is wave refraction. This happens as the waves move from deeper water into shallow water, the forward speed of the wave slows down. The portion of the wave still in deep water is traveling faster, and as it encounters the bottom, it too slows. This is why waves appear to take the shape of the shoreline as they approach wave refraction. When a wave hits a solid object such as a seawall, jetty, island, or some other solid structure, the wave is reflected off the object in the opposite direction with little loss of wave energy.

[abarnes]

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[Viet Thy]

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