They are rare and small here but they do happen occasionally.  The one this morning woke me up and was followed by a small aftershock around noon.  I'm guessing the increasing frequency of these small quakes is related to the Barnett Shale drilling that has been going on around here the last few years.  Looks like the location is in the Trinity River bottoms between Grapevine and Euless where there are several pad sites and lots of frac-ing.

From the USGS website

Magnitude 3.3
Date-Time Saturday, May 16, 2009 at 16:24:06 UTC
Saturday, May 16, 2009 at 11:24:06 AM at epicenter
Time of Earthquake in other Time Zones
 
Location 32.796°N, 97.091°W
Depth 5 km (3.1 miles) set by location program
Region NORTHERN TEXAS
Distances 6 km (4 miles) S (179°) from Euless, TX
7 km (4 miles) SE (141°) from Bedford, TX
9 km (6 miles) ESE (118°) from Hurst, TX
11 km (7 miles) NNE (16°) from Arlington, TX
28 km (18 miles) W (269°) from Dallas, TX
 
Location Uncertainty horizontal +/- 9 km (5.6 miles); depth fixed by location program
Parameters NST= 11, Nph= 11, Dmin=44.5 km, Rmss=0.86 sec, Gp= 94°,
M-type="Nuttli" surface wave magnitude (mbLg), Version=6
Source USGS NEIC (WDCS-D)

 
Event ID us2009gsba