If these earthquakes are caused by fracking, it would be more akin, to an underground avalanche, me thinks.. I don't believe fracking could cause enough pressure, to move the earths plates.
Fracking can go quite deep, it's putting a liquid/steam into the ground and when the pressure becomes too much, it causes the oily matter to liquify, causing them to raise to the surface, or follow the path of least resistance, generally up the pipes supplied for it to do so. The material being taken from the ground is replaced by another, liquid.
Have you ever heard of the teacher that fills a big glass jar with big rocks, then asks the class is the jar is full?
They think it is.
Then he fills it with smaller rocks, then sand, then water. When he gets to that point, he decides the jar is full.
It is full, but it is NOT, however, solid.
Neither is the rock with oil in it. Most of the oily material is sponge like.
This is why, I think what is happening on the east coast is more like an underground avalanche, if anything. There are layers of rock that are not solid, add the fracking and it could cause some collapses, or slides. Is this what the rumbles are? I have no idea. They'd have to measure the depth of the "earthquake" and pinpoint it's epicentre. Could it just be a weak spot in the crust or is it caused by excess pressure, we are applying or is it natural? To little information to know at the moment. I'll be interested to hear more than conjecture.