What is the difference between the focus of an earthquake and its epicenter?

2 answers

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?
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.