Download Onshore, active source seismic data were collected along two dip

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.