The seismicity of Oklahoma is an interesting and unfolding story - in the last few years the number of earthquakes with magnitudes greater than 3.0 has increased significantly. Although Oklahoma has a history of moderate-size earthquakes dating back many decades (an estimated magnitude 5.5 occurred on 09 April, 1952 near El Reno). The rate of small-magnitude earthquake activity in the central and eastern US increased first around 2003 (USGS), and then again in late 2009. Much of the 2009 increase may be associated with activity in Oklahoma, which increased sharply in 2009:

The M≥3.0 activity rate for Oklahoma from about 1975 to 2008 was roughly constant. The recent activity is believed to be related to fluid injection into the subsurface, which is known to trigger small-to-moderate size earthquakes (USGS page on induced earthquakes), and believed to have at least indirectly played a role in the largest earthquake of the recent OK activity, an Mw 5.6 earthquake that occurred near Prague, OK in 2011. Like the Prague earthquake, most of the smaller activity seems to be caused by the triggered release of tectonic stress that includes a roughly east-west oriented horizontal compression (see the earthquake information on the Saint Louis University Earthquake site).
Two M4.3 earthquakes and numerous small events occurred last night in Oklahoma, just south of the town of Marshall, located north of Oklahoma City, and a M4.4 occurred this morning (these are USGS mbLg values, those of the Oklahoma Geological Survey are slightly different). Here's a map of earthquakes from the last 30 days (as of 12:30PM EDT). The red circles show the more recent events, then the orange, the yellow are more than a week old. The circles in the northwest occurred last night.

Here's a close up of the recent events on a satellite view - not many people in the area, but the town of Marshall is only a few kilometers distant.

Seismograms
The seismic station Liberty Lake, which is located just south of the town of Guthrie, is the closest station (about 60 km to the south-southeast). Here is a channel list for the station:
GS; OK029; 00; HHZ; Up-Down, Liberty Lake, OK, USA
GS; OK029; 00; HH1; North-South, Liberty Lake, OK, USA
GS; OK029; 00; HH2; East-West, Liberty Lake, OK, USA
A list of other stations was posted a few days ago (see the previous post).
A plot of the displacement seismograms for the first M 4.3 is shown below (you can right-click on the image to open a larger version in a new window so that you can see the details better). Note that the times in the display are UTC, the local time reference is my local time - eastern US. At the Liberty Lake Station, the signals were largest for the first event, then the third event, and the middle event signals were slightly smaller. This may not be the same at other stations, and the magnitudes are computed using many more that one station.

Not surprisingly, the displacement seismograms from the later event look similar (but not exactly the same).

Here are the seismograms from the most recent, M4.4 event. Again, the shape is very similar, but a careful look shows subtle differences.

If you look closely, you'll see that the signals from the M4.4 event are a little smoother than those of the earlier events, which is consistent with it being slightly larger and having a slightly longer duration, which subtlely smooths the signals. Of course a subtle observations such as this could also be a result of a slightly different propagation paths of azimuths from the source to the receiver.
Near-Station Site Resonances
The displacement seismograms are obtained by integrating the ground velocity seismograms returned from the waveform server (press and hold on the seismogram display for a menu with this option). A number of resonances, probably associated with the near-surface geology beneath the seismic station are obvious in the signals. Here are the seismograms for the later event returned from the seismogram server (these are proportional to ground velocity).

The P-wave reverberations, observable on the up-down component of motion just after the initiation of motion, has a repetition time of about 1.0 seconds, the shear-wave reverberations, observable with the three peaks on the east-west component of motion starting just before 08:42:50, repeat about every 1.8 seconds.