How do you know an earthquake is about to happen

You can't really predict it but if you have an animal they can sense when it's coming by they're body language

Explanation:

Seismograms come in handy for locating earthquakes too, and being able to see the P wave and the S wave is important. You learned how P & S waves each shake the ground in different ways as they travel through it. P waves are also faster than S waves, and this fact is what allows us to tell where an earthquake was.

there are some featured computer there are used to find out earth quake. in olden time there where seismogram. please don't forget to follow me

answer called a epicycle;