do earthquakes occur in areas without identified large faults?
The key words you use are "identified" and "large." As far as I know, earthquakes occur at fault lines, whether or not they have been identified or are large.
Since this is not my area of expertise, I searched Google under the key words "earthquakes faults" to get these possible sources:
http://www.tinynet.com/faults.html
http://hometown.aol.com/jillconway/quakes.html
http://earthquake.usgs.gov/learning/faq.php
http://www.earthquakecountry.info/roots/basics.html
http://www.gns.cri.nz/what/earthact/earthquakes/earthquakefaq.html
I hope this helps. Thanks for asking.