Sometimes they will give you that info on the calif quake map - but not for the little ones - I think to figure it out you need to analyze the various recording stations, determine whether dilation of compression is going on at each site, plot that data and look at 'the beach ball'

Here's a good explanation of 'the beach ball' and how a focal mechanism is determined.
http://quake.wr.usgs.gov/recenteqs/beachball.html

Canie

• Focal mechanisms