Explain why the portions of the San Andreas fault that are locked ...

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Explain why the portions of the San Andreas fault that are locked are or are not safer than the parts
  where the two plates slide more or less continually. What is the name of the theory that deals with this
  issue? What will be an ideal response?

Question 2

What causes tsunamis, and why are they so destructive? What will be an ideal response?

[Moriaki]

Answer to Question 1

The locked portions of a fault are probably less safe than those that slide regularly. The locked
portions are storing energy in the surrounding rocks, which will ultimately be released in a large
earthquake. The portions that slide frequently build up much less energy, since they release it
frequently. The name of the theory is the seismic gap theory.

Answer to Question 2

Many tsunamis are caused by the displacement of ocean water caused by crustal movement or
slumping as the result of faulting. They are very destructive because they are incredibly fast-moving
waves with long wavelengths. These waves reach large sizes only where they enter water shallow
enough for them to touch bottom (1/2 wave length), and thus the wave amplitude increases.