What happens to P- waves and S-waves when they encounter the ...

[CharlieWard]

What happens to P- waves and S-waves when they encounter the core-mantle boundary, and what does
  this change in behavior indicate about the core? What will be an ideal response?

Question 2

Why has it been suggested that large earthquakes might be prevented by injecting water along isolated
  portions of fault zones that have been inactive for an unusually long time? When was this technique
  discovered? What will be an ideal response?

[ju]

Answer to Question 1

P-wave velocity abruptly decreases, and S-waves disappear, meaning that at least the outer core must
be liquid

Answer to Question 2

Local increase of fluid pressure can cause small earthquakes, which release stresses that would
otherwise build up to cause a larger earthquake. This phenomenon was first recognized when it was
discovered that liquid waste disposal by deep well injection at the Rocky Mountain Arsenal near
Denver, Colorado, was responsible for numerous small earthquakes in the area.

[CharlieWard]

Thanks for the timely response, appreciate it

[marict]

Excellent