Well, the force is proportional to the product of the charges
on the two objects. So if the objects are already negatively
charged distance between them is unchanged, then adding
electrons to either or both objects would increase the forces
between them.
You can't answer this question because you aren't giving the specific type of seismic waves. There is an s-wave a p-wave and an l-wave. Those are the basic waves. An S-wave cannot travel through a liquid at all. So, obviously it travels slower than any other seismic wave.
<span>It would travel faster because their speed depends on the density and composition of material that they pass through.</span>