What is the minimum number of seismic monitoring centers needed to provide the data for triangulation?

3

Explanation:

The answer is within the question since it talks about triangulation a triangle.

The principle is that from each station, you get a distance location from that station of the event. Then from each center you make a circle with the distance measured at that center.

All three circles done form the monitoring centers will meet at a point somewhere between those three centers, and you'll get your location.

That's the triangulation process.  You do need 3 points for a precise reference, if you have only 2, you are left with 2 possibilities.

for e2020. the answer would be some directions from the mountain range so we can find mt. whitney. to locate which direction is north, you should use a   compass. this would not only find mt. whitney, but also becuase of this long paragraph you would get points because it's not like anyone actually reads your work becuase once they read the first sentence it sounds dumb enough to not read becuase i'm not good at answering this but the answer is compass for your benefit.

for e2020 ; -;