Here is an interesting paper(pdf) that looks at seismic communication. It shows how elephants and large animals can communicate by through stomping and sending signals through the ground.
What's interesting is that the paper says, "humans may once have used seismic stimuli as a mode of communication when the ground was a quieter environment." They test this by having a 170 pound person jump on the ground. It turns out that the jump creates a seismic disturbance measurable at up to 1 kilometer away.
The paper also details how animals (and humans) have mechanoreceptors that allow them to perceive vibrations through their feet.
