I like looking over the 24 hour charts and looing for interesting things and I have seen a few times these very low frequency (<1hz) one cycle waves that are stronger than most of the vibrations. They only have one cycle and do not taper in or out.
For some info on where the shake is located: It is on the cinderblock foundation to the detached garage (I will move it to the concrete slab once I extend the power cable and Lan cable). I do live in a relatively noise environment during the day with traffic and retail business around, but it quiets down a lot at night.
Has anyone else seen anything like this? I don’t believe it to be anything electronic related as I would expect to see more oscillation in the signal, and I would think it is too quick for the earth below the garage to be swelling.