Was there really an earthquake in San Francisco? I heard it was 3.9 or something but I don't know if its true, no one will tell me.
Yes. See the list, conducted by the United States Geological Survey (USGS):
http://earthquake.usgs.gov/earthquakes/recenteqsus/Maps/special/California_Nevada_eqs.php
In it, we see: Magnitute 4.0, time (UTC) 2011/10/20 21:41:04,
location 3km South-East of Berkery, California.
(addition)
I found that a local news site reports it:
http://www.huffingtonpost.com/2011/10/20/san-francisco-earthquake_n_1022945.html
It says, there are no damages or injuries.
