There must be a thousand other variables. Like for example would all 600 million people have to be standing next to each other in like one big mass? Or 600mil anywhere within a large radius? What about altitute and thus different pressures? What about the material of earth? For example if someone jumps and lands on sand, that would be less force against earth then a person on concrete, where his weight is spread over a larger area.
I'm not very scientific, I don't know any fancy formulas, but picture this okay?
600 million people, all standing next to each other, at 0 altitute, on a hard surface of earth. Everyone jumped the same height and landed at the same time. Now how does an "impact" like that, compare to, say, a meteor hitting? Like what would the diameter be of 600 million people standing in a circle? Picture all those people as like a big hammer against earth.
What is interresting is, when two objects collide with equal force, they cancel each other out. This HAS to be, or else one object would always be pushing the other object to move. Also, if one object is stationary, and able to resist certain forces, it can't be moved. Like if you put both your hands together in front of you and push equally with both arms so that your hands stay still, this is equal force. But then walk up to a block wall and lean on it. If you're leaning 20 pounds against the wall, it is pushing 20 pounds back at you. If you push 150 pounds, it pushes 150 pounds. So until you push more then it can resist, it will stay still and neither of you will move. But if you push 1000 pounds, that wall may push over, and you don't cancel each other out anymore.
So then, what possible difference can ONE person do, jumping? And then multiply that by 600 million. The earth, by far, has enough resistance to cancel such force. Especially if the force is spread over so much space as "western hemisphere".
It is interresting to think about though