Ongoing seismicity in the Dallas-Fort Worth area

We report on and discuss the continuous seismic activity in the Dallas-Fort Worth (DFW) area. There was no reported seismic activity by USGS/NEIS until 31 October 2008, approximately seven weeks after the start of salt-water disposal at a nearby injection well in the southern part of the DFW airport. The salt-water disposal injection ceased in August 2009. The event detection based on crosscorrelation between several template events from DFW area and continuous seismic record shows that the seismic activity has been continuous for more than three years. Continuous monitoring at a local station allows us to complete the catalog down to a magnitude of zero, providing more detailed information on seismicity in the DFW area. This seismic activity migrated in space from a cluster southwest of the injection well to a cluster 2 km northeast of the injection well after May 2010. We show that the crosscorrelation detection at the WMOK regional station is not able to detect both south and northeast clusters of events without using multiple template events. Furthermore, we show magnitudes of the largest events increase since May 2010.