Abstract

Dipping reflectors in oceanic crustal seismic reflection profiles have been attributed to either faults cutting through the crustal section or magmatic layering in the mid- to lower crust. Using closely spaced (<1 km) single-channel seismic and multichannel seismic profiles collected near Ocean Drilling Program Hole 504B, we show that a conspicuous dipping event previously interpreted as a low-angle fault striking perpendicular to the ridge axis is actually a scattering artifact from an ∼ 80-m-high, sediment-buried basement fault scarp located ∼ 2 km south of Hole 504B. The interplay between the orientation of the profile relative to basement topography and the streamer feathering angle can significantly increase the moveout of scattered energy above the sediment-basement root-mean-square velocity, allowing these scattered events to stack coherently at crustal velocities. These results suggest that in many cases dipping events imaged in oceanic crustal reflection profiles may be scattering artifacts rather than real geologic features.

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