Um... I've no idea what happened there, but if I recall correctly I was trying to post about an odd sound/sensation which occurred. So let's try again...
That afternoon (the day before my aborted post) I was sitting at home, Mr Zebra had taken the dogs for a walk. There was a loud thud/boom sort of sound, but most importantly though it was accompanied by a distinct, but very brief, feeling underfoot. If you've ever lived in a semi-detached house of dubious construction (think 60s/70s council houses here in the UK or - very probably - modern housing) then you'll know of the effect of a door being slammed and the slight feeling of shaking of floorboards which accompanies it.
It felt exactly like that. Except; we live in a detached house, and its construction most certainly does not lend itself to shaking.
But that's what I felt. In fact, that's what immediately came to mind (in that very quick way that one's brain provides a solution) before I realised that logically it could not have been that.
When Mr Zebra returned from his walk I told him about it; curiously he had also heard the sound but had not felt any shaking underfoot. He could not (and still can't; I've just asked him) define either what sort of sound it was, or what direction it had come from. But heard it he had; while in the park not too far away from our house (and therefore standing on grass - in case that makes any difference to the lack of shaking on his part).
So; that's it - not particularly exciting I know, but it remains an odd mystery. Not the sound itself per se; as there can be many explanations for odd sounds (although neither of us know what it was to this day, and have not heard it since) - but mainly why on earth I felt it underfoot as I sat at home remains quite bizarre.
I shall note that nothing shook or otherwise moved during the brief moment that I felt and heard the sound, and we do not live in an earthquake zone as far as I know
Thoughts and/or similar experiences greatly received...
Could be contractors driving piles into the ground, although usually you would expect more than one incidence (you may have missed others). Happened to us when pile driving being done 50m away. Floors vibrated and booming sound. Environmental Health said it was within "acceptable" levels.. If you live near a railway line a very heavy goods train can produce that effect in certain circumstances as will a heavy wagon driving through a large pothole. Had all that myself. Amazing how sound and vibration can travel underground. You can check for seismic activity in the area on tinterweb. (British Seismic)