how to know when a earthquake come in action ??

Answer 1

When the ground starts to shake, I suppose. The Earth's tectonic plates rub against each other and cause shockwaves to move through the ground.

Are you sure you are finished with this question? Come in action to what or for what?

Answer 2

i guess your question is "how does it feel like during a earthquake?" well i've never been through an earthquake but i've been watching specials on it this whole week on national geographic. they say first you begin to feel the ground start to woble (kinda like that feeling when you feel the ground swaying when you're sitting at the upper levels of a giant stadium), the this swaying increases to a point where the ground is literally rippling like a giant jello bowl. after a few minutes the wobble starts to discipate and there will be some minor aftershocks after that. hope this info helps.

Answer 3

I think you mean, "How can we know when an earthquake will happen, before it starts?" That is, "How can we predict an earthquake."

Well, we can't. They are trying to come up with something that helps out with that, but so far, no luck finding out what will indicate that an earthquake will happen.