My post yesterday regarding a 3.3 magnitude (which is an update to the originally reported magnitude of 3.1) earthquake in central Oklahoma has generated several e-mails inquiring about the recent seismic activity in the Sooner state.
The above map shows the locations of earthquakes over the past week (in yellow) and month (in light blue). The 2 red squares show the quakes that took place on Saturday. As you can see, the bulk of this activity has been centered in an area near Jones, which is about 20-25 miles East/Northeast of Oklahoma City (in the lower left corner of the map), to the North of Highway 62 and South of I-44.
The Oklahoma Geological Survey has dubbed the recent activity the "Jones seismicity". This uptick in activity actually began in 2009, with 27 quakes were reported in the area (before 2009 a total of only 7 earthquakes had ever been reported in this area). The strongest so far took place on January 15 2010, when two quakes, one a magnitude 3.8 and the other a magnitude 3.7 took place within 9 minutes of one another, again near Jones.
In Oklahoma, "minor" earthquakes are often caused by oil drilling/excavating activities. The activity near Jones, however, is not consistent with this trend because of the lack of drilling and excavation in the area. Instead, it is more likely to be associated with truly natural seismic activity that, for some reason, has been increasing in the region for the past year.
For more information on Oklahoma earthquakes, including the examination of increased activity near Jones, here is an excellent website from the Oklahoma Geological Survey in Leonard.