Lance Hart, 51, said he heard "some rumbling that sounded a bit like thunder" outside his Darwin River home on Thursday night.
"I thought 'what on Earth are the neighbours doing, they're 800 metres away," Mr Hart said.
"But it was night time, out in the rural area, and I couldn't see anything and didn't give it much thought after that."
Mr Hart said he "carried on with life" and work before returning to the site on Saturday.

"I just thought, 'holy shit'."
Mr Hart said a huge sinkhole - about 40 x 30m wide and at least 15 metres deep - had appeared and swallowed "massive trees".
"There was water at the bottom, it must have been very deep because one of the trees was really big, about 2.5ft across, and there's no sign of it, it's gone," he said.
"There were a couple of other fairly large trees that have gone without a trace as well."
"My son was speechless," he said.
Mr Hart said there was also "a big crack in the ground where (the land) had slipped".
He said there used to be a "slight ditch" - the bed of a dried up billabong - in the spot where the Earth opened up and left a gaping hole in the ground.
"But it's going to be interesting to see what happens next wet season when the sink hole fills up with water and the loose edges start to slide," Mr Hart said.
"I think it's a matter of wait and see what happens, it's just a natural phenomenon ... sink holes happen."




The answer is obvious: A burst water mains! Therefore all the water at the bottom. Case closed! Yes sometimes these watermains turn up in the most unusual places, deserts and what not and at huge depth, but still, after careful investigation by the usual competent authorities the answer will be clear. Zzzzzzzzzz