posted by Shirley .
What is the difference between the focus of an earthquake and its epicenter?
An earthquake occurs far from an observing station and produces P, S, and surface waves. Do all the wave arrive at the same time? If not, which arrives first and which last?
Try some of the following links for in formation on your first question:
Then refer to your later post about the 2nd question, because I saw and answered that one first.
The focus of an earthquake is the point below the Earth's surface from which the earthquake (seismic waves) appear to originate.
The epicentre is the point on the Earth's surface directly above the focus.