Seismicity in the Triassic Deep River Basin, North Carolina

The Deep River Basin in central North Carolina is one of a series of Triassic rift basins along the east coast called the Newark Supergroup. Although the east coast lies on a passive plate margin, there is recorded seismicity within all of the coastal states, much of which is attributed to boundary faults of the Newark Supergroup basins. However, this seismicity is conspicuously absent around the Deep River Basin and most of North Carolina east of the Appalachian Mountains. In March 2012 we installed a 12 station broadband seismic network surrounding the Sanford Sub-Basin of the Deep River Basin to measure unrecorded seismicity. Through fifteen months of data collection, we have confidently detected and located more than 160 low magnitude seismic events within the array. However, the event locations cluster in four locations - three of which are near local rock quarries and one is near an unidentified anthropic feature. Further, these events consistently occur between the hours of 9am and 6pm local time, Monday through Friday indicating that they are anthropogenic. The Deep River Basin is one of the most likely places east of the Appalachian Mountains in North Carolina to be seismically active, yet we have measured no natural seismicity. Using receiver functions and known origins of the local seismic events we will be examining the crustal structure beneath the Deep River Basin to explain the conspicuous lack of local seismic activity.