Here's my entry for Hazard-of-the-Month-Club:
http://www.northcountrypublicradio.org/news/story/23659/what-s-that-noise-could-be-a-cryoseism

Apparently at very low temperatures ice expands with enough force to actually register on seismometers up to about Richter 1.5. I'll bet our Minnesotans sleep right through something like that. But it is something to shake up the exceptionally calm Canadian Shield (said with envy from real earthquake country).

Cryoseism -- a better explanation than aliens landing in your neighborhood.

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