# How do seismologists locate the epicenter and focus of an earthquake?

I know the focus of an earthquake is where the earthquake originated from, but what I could never figure out is, how to scientists find out where exactly the focus (and epicenter) are located?

• Triangulation, the same way GPS satellites are used to locate something on the surface of the Earth. You use multiple seismometers (3 or more), and the arrival time differences between them tells you how far away the source point was. There is some complication because of inhomogenaities in the Earth causing scattering and deflection of the seismic waves. – Chris Mueller May 2 '14 at 19:37
• I think this is the kind of question where some research effort should be shown. – tobias47n9e May 2 '14 at 20:23
• Did you intend to down vote the question or the answer? – Mark Rovetta May 2 '14 at 20:40
• Actually downvoted both :) - But now only the answer. Your comment does make sense and the link is very educational. So I hope Jaxon can edit his question to "What are good learning resources to find the epicenter and focus of an earthquake?". Then I would also upvote the question again. – tobias47n9e May 3 '14 at 7:28
• @MarkRovetta - I actually mixed up the words in my comment. I upvoted the answer but downvotet the question. – tobias47n9e May 3 '14 at 10:07

• Seems better; you might want to add a bit more (you could even quote the page via a blockquote >!). – hichris123 May 5 '14 at 20:33