I saw a news piece a few weeks ago about this idea and I think this article refers to idea they were discussing: http://news.sciencemag.org/earth/2015/04/smart

I saw a news piece a few weeks ago about this idea and I think this article refers to idea they were discussing: http://news.sciencemag.org/earth/2015/04/smart-phones-could-be-used-detect-earthquakes http://news.sciencemag.org/earth/2015/04/smart-phones-could-... I would guess that there are enough phones plugged in at any given moment, even during the day, to provide a large enough sample size. Especially if that were paired with other data sources.