EVIDENCE FROM HOLE 504B FOR THE ORIGIN OF DIPPING EVENTS IN OCEANIC CRUSTAL REFLECTION PROFILES AS OUT-OF-PLANE SCATTERING FROM BASEMENT TOPOGRAPHY

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 colle cted near Ocean Drilling Program Hole 504B, we show that a conspicuous dipping event previously interpreted as a low-angle fault striking pe rpendicular to the ridge axis is actually a scattering artifact from a n similar to 80-m-high, sediment-buried basement fault scarp located s imilar to 2 km south of Hole 504B, The interplay between the orientati on of the profile relative to basement topography and the streamer fea thering angle can significantly increase the moveout of scattered ener gy above the sediment-basement root-mean-square velocity, allowing the se scattered events to stack coherently at crustal velocities, These r esults suggest that in many cases dipping events imaged in oceanic cru stal reflection profiles may be scattering artifacts rather than real geologic features.