Can someone explain briefly how quakes and aftershocks differ? How do they determine whether it’s a quake or an aftershock?
I believe it's based almost entirely on location and time. If there's another seismic event in the same location after an earthquake within a reasonable period of time (which could be months), then it's labeled an "aftershock". If you had a larger seismic event than a previous earthquake, that previous earthquake could then be labeled a "foreshock".
So for instance, you could have a 8.2 earthquake, and a month later have a 7.9 earthquake in the reasonable proximity of the first (and on the same fault line), and that second large quake would still be technically described as an aftershock.
Technically speaking there is no difference. An earthquake is an earthquake. “Aftershock” is a man-made definition used to categorize earthquakes that occur within a certain a timeframe and location.