Question: how do you identify earthquakes?

Tim Craig answered on 18 Jun 2018:

Great question. There are a few ways we can do this, but the most common is using seismology. Basically, when an earthquake happens it sends out shockwaves through the Earth. If you’re near the earthquake, you feel these as the ground shaking beneath you. The further away you are, or the smaller the earthquake is, the smaller these waves are. But with really sensitive instruments, we can detect the waves sent out by even small earthquakes all the way around the world. I you detect waves arriving at a range of places around the world, you can use the time at which those waves arrive to work out where and when the earthquake occurred. We can also use the strength of those waves to work out how big the earthquake was, how long it lasted, and a whole range of interesting things related to what caused the earthquake, the physics behind it, and the structure of the Earth.