[Mariebl]

Same question about and after shock … how do we know that something called and “after shock” is not another earthquake?

Basically, they do an after-the-fact analysis of the situation. Start with the original earthquake. If afterwards, you have a succession of smaller earthquakes, those are aftershocks. However, if you have a larger earthquake after your original quake, then the first quake is then referred to as a 'foreshock.'

I know that this doesn't sound very scientific, but we have a lot to learn about earthquakes. To have a better determination of aftershock/foreshock, you'd have to understand the causes well enough to predict them, and we're far from that.

(I've felt three quakes in the last month that were approximately 4s--mild, but it raises my adrenaline level.)

[doc1019]

Thanks, any information is information that improves my knowledge library.