Possum, this doesn't answer your question but I found it interesting. It shows all the earthquakes in Oklahoma between 1977 and 2001. The earthquakes shown in red are the ones strong enough to be felt.



Edit: I just found this for 2009.

OKLAHOMA GEOLOGICAL SURVEY OBSERVATORY
OKLAHOMA EARTHQUAKE CATALOG 2009

DATE TIME (CT) COUNTY ST MM MAGNITUDES LATITUDE LONGITUDE DEPTH SM
YYYY MMM DD HH MM SS.SS 3Hz bLg km

2009 JAN 28 05:19:09AM GRADY OK F 3.4 35.163N 97.871W 5.00
2009 JAN 29 07:03:00PM LINCOLN OK F 2.4 35.724N 96.920W 5.00
2009 FEB 03 04:23:00AM COAL OK F 3.2 34.580N 96.369W 5.00
2009 FEB 22 03:43:07AM GARFIELD OK F 3.2 36.353N 98.098W 5.00
2009 MAR 08 08:06:39AM OKLAHOMA OK F 3.6 35.452N 97.479W 5.00
2009 MAR 17 12:25:19PM OKLAHOMA OK F 2.7 35.446N 97.456W 5.00
2009 MAR 17 12:41:37PM OKLAHOMA OK F 2.5 35.446N 97.456W 5.00
2009 MAR 17 02:57:15PM OKLAHOMA OK F 2.4 35.446N 97.456W 5.00
2009 MAY 28 08:26:28PM LINCOLN OK F 2.2 35.80N 97.00W 5.002009 JUN 14 15:31:08 LINCOLN OK F 3.4 35.624N 96.854W 5.00 2009 JUN 16 10:32:46AM LINCOLN OK 2.8 35.890N 96.872W 5.00