The place in the Earth where an earthquake begins is called the focus.
The point on the surface directly above the focus is called the epicenter.
The epicenter is where people feel an earthquake most strongly. Scientists
have set up instruments all around the Earth to measure earthquakes.
These instruments record the ground movement where they are, as the
shaking from an earthquake travels out in waves from the focus where
the earthquake began. By combining this information with data about
how fast waves travel through the earth, scientists can figure out
where and at what time an earthquake occurred, and how strong it was.
A seismograph records earth movements during