ABSTRACT

We utilize Transportable Array data to survey regional seismicity in east Texas and northwest Louisiana. Through analyst review and a waveform‐matching technique, we identify 58 earthquakes occurring between April 2010 and July 2012. The earthquakes spatially cluster within two main zones, near Timpson, Texas, and within Bienville Parish, Louisiana; minor clusters occur in the Texas–Louisiana border region. Although the Timpson earthquakes have been studied previously, we identify many undetected earthquakes that occurred in 2010, about two years prior to the 17 May 2012 Mw 4.8 earthquake, which has been linked to wastewater injection. The Bienville Parish sequence, which consists of magnitude 0.5–1.9 earthquakes in mid‐ to late‐2011, occurred about 10 km from wells that began injecting at relatively modest rates (∼40,000 barrels (bbl) per month) in late 2010 but within a few kilometers of production wells that were being hydraulically fractured around the same time period. An additional cluster of seismicity was observed, near Center, Texas, with some seismicity occurring in the months prior to the start of wastewater injection and the largest earthquake in that sequence occurring when injection exceeded 200,000  bbl/month; this may be a case in which injection into a seismically active area promoted a larger earthquake. Finally, there was also seismicity observed near the Toledo Bend Reservoir in Louisiana. The evidence concerning some of the sequences indicates they might be associated with either hydraulic fracturing or recent increases in wastewater injection at wells within the unconventional Haynesville shale gas play. The results of this study highlight the need for more extensive seismic monitoring in the central and eastern regions of the United States of America.

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