Ed T.

Fascinating. Mind you, the tectonic plates have to be taken into account. They have considerable mass and can dampen the forces built up by sex.   

Notwithstanding you use more energy (for the bloke that is) doggy fashion than missionary, (and rodeo, don't forget the energy used in rodeo, which is like doggy fashion but once you get started you tell her she is almost as good as her sister...) and yes, considerable energy is translated into kinetic means resulting in a certain amount of g, (the ratio of force to load.)

Sadly, the force is lazy couples going through the motions and the load is at least the mass of the tetonic plate you are on and pro rata the counter effect of that on the mantle and core of the earth.

Result? Inconclusive. Back to the bedroom to conduct further tests. Objective 1. Eat fish and chips to increase the g. Objective 2. See if you can get her to drop her bag of chips - this would mean success of another kind.