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Onshore, active source seismic data were collected along two dip lines in the summer of 2015 on the mid-Atlantic coast for the Eastern North American Margin (ENAM) Community Seismic Experiment (CSE), funded by NSF GeoPRISMS program as part of the Rift Initiation and Evolution (RIE) Initiative. The study area encompasses the Carolina terrane, the Piedmont, and Atlantic Coastal plain in eastern North Carolina and southeastern Virginia. Data were acquired using a total of 11 explosions, five on the northern profile and six on the southern profile, and recorded using 720 Reftek-125 “Texans” with a 250 m spacing along ~220 km profiles. This instrument spacing yields Pg arrivals along each entire profile, PmP arrivals on offsets greater than 100 km, and Pn arrivals on offsets greater than 120 km. Preliminary 2-D velocity models along both profiles reveal a crustal thicknesses between 35-40 km and show a high velocity (>7.0 km/s) layer at the base of the crust coincident with crustal thickening to the east. This feature may represent magmatic underplating and is also observed along the margin to the north of the ENAM-CSE study area. Refining the velocity structure of these models will aid in determining the location, thickness, and timing of intrusive magmatic events, as well as investigate the relation of magmatism, crustal thickness, and underplating along the margin. Because of the complex tectonic history of the margin, characterized by multiple episodes of terrane accretion, orogenesis, magmatism, and rifting, these results will aid in understanding how mechanical deformation and mantle melts interact during continental rifting, and can help constrain how these interactions lead to continental breakup. Depth (km) Distance (km) Seismic Velocity (km/s) Figure. Preliminary 2-D P-wave velocity model along ENAM CSE Line 1 with a contour interval of 0.5 km/s. Crust thickens from ~35 km in the west to ~40 km in the east, with a high velocity (>7.0 km/s) layer at the base of the crust.