Near surface structures across the Brevard fault zone are studied using the refraction and reflection arrivals recovered from the Appalachian Ultradeep Core Hole (ADCOH) regional seismic Line 1. In using refracted arrivals, a new processing approach is introduced that translates refracted first arrivals from multifold seismic data into a refraction stack of two-way delay time sections. Reprocessing of reflected arrivals has improved shallow reflectors and allowed better imaging of the Brevard fault zone. Following processing of refraction and reflection arrivals independently, both data sets are combined into a <u>composite stack</u> section. The composite stack section displays one bright refractor interpreted as the boundary between the weathered layer and high velocity crystalline rocks. This refractor is continuous in the Inner Piedmont with occasional vertical offsets. The continuity of the refractor diminishes across the Brevard fault zone. In the eastern Blue Ridge, the refractor is discontinuous with high angle truncations. On the composite stack section, the Brevard fault zone can be traced from the surface to 6 km (2 s) where it appears to splay from the Blue Ridge thrust. Different from previous interpretations, the Brevard fault zone is imaged as having both an upper and a lower boundary surface as well as a group of reflectors within the zone. This reflection package initially thickens to 2 km at 3 km depth, then thins as it reaches the Blue Ridge master decollement. The Blue Ridge thrust is as shallow as 1.5 km (0.5 s) at the northwest end of the Line l. A deeper decollement is interpreted below the Blue Ridge thrust. The depth of this deeper thrust is 3 km (1 s) at the northwest end of the line, and also joins to the Blue Ridge thrust at 6 km depth making the structures below the Brevard fault zone more complex than previously published. / Master of Science

A new interpretive slow-varying (long-wavelength) static estimation method is introduced to remove the effects of static anomalies caused by lateral variations in near-surface velocity. The application becomes critical where the wavelength of the variation of statics is larger than the maximum offset between source and receiver (spreadlength) used during data acquisition. The method used in this study utilizes the reflection and refraction arrival times from the shallowest reflector or refractor to determine the statics variations. The study include reprocessing of 12 seismic reflection data sets from the Savannah River Site area, near Aiken, South Carolina. The same data sets were also used to extract the refracted arrivals by the refraction stack processing. Application of the estimated slow-varying statics enhanced the S/N ratio, lateral continuity, and coherency for deep as well as shallow data and allowed to better determine the geometry of faults in the Coastal Plain sediments, which penetrate from the basement. Interpretation of the enhanced seismic reflection and generated seismic refraction sections helped to constrain the depth of upward penetration of the faults imaged in the seismic data. Refraction stack sections were used to obtain better definition of the delineation of the upward penetration of the faults at shallower depths. Despite the smoothing effect that is incorporated in the refraction stacks due to long refracted paths they exhibit clear-cut termination and offset on some of the lines in spatial zones where the Pen Branch fault can be projected in the shallow sediments. The seismic data indicate that the Coastal Plain sediments dip and thicken toward the southeast in the area. The basement top provides a high acoustic impedence contrast, and has a regional dip towards the southeast. The Pen Branch fault is one of the longest faults in the area, that acts as a basin bounding fault separating the Paleozoic crystalline basement from the Triassic basin fill. Other faults such as the Steel Creek and A TT A have also been discerned by the seismic data in the area. Small antithetic faults appear to join the Pen Branch and the A TT A fault. The offset of the Pen Branch fault (15 ms; 32 m) is relatively higher then the offsets observed for the ATTA (11.5 ms; 24.5 m) and Steel Creek (13 ms; 27.5 m) faults. The delineation of the upward depth of penetration of the Pen Branch fault is imaged best on lines 28 and 2EXP where the reflections at 0.18 to 0.2 s exhibit termination with amplitude changes, thereby suggesting the presence of the fault at that level. The offset associated with the A TT A fault can be traced up to 0.16 son line 27. The expression associated with the Steel Creek fault does not seem to go above 0.2 s. On the basis of the result from the interpretation of line 27, the upward depth of penetration of the A TT A fault in the Coastal Plain sediments reaches to a higher level then that of the Pen Branch fault. On the basis of the reflection and refraction data it is interpreted that the reactivation of the Pen Branch and the A TT A fault is as young as the age of the shallow reflector at 200 ms (top of Cretaceous?). / Master of Science

Complex trace attribute analysis has been applied to 24-fold VIBROSEIS reflection data acquired on the Atlantic Coastal Plain near Charleston, S. C., to yield an expanded interpretation of a Mesozoic basin concealed beneath Coastal Plain sediments. Complex trace attributes express the seismic trace in terms of a complex variable and emphasize different components of the original seismogram. Attributes derived from synthetic seismograms of thin beds are used to interpret the patterns observed on the real data. Complex trace attributes derived from the original seismic trace complement the interpretation of a Mesozoic basin originally imaged by conventional data. The combination of single-sweep recording and use of complex trace attributes is believed to support an interpretation of a transition from basin border conglomerates into finer-grained siltstones nearer to the center of the basin. / Master of Science / incomplete_metadata