“…Away from fracture zones, laminated zones and dipping reflectors spaced 5-to 10-km apart appear in lower crustal portions of multichannel profiles (NAT Group, 1985;McCarthy et al, 1988;White et al, 1988). On slowspreading ridges, refraction data indicate that the variability of crustal and Moho seismic structure increases near fracture zones (Detrick and Purdy, 1980;Cormier et al, 1984;Mutter et al, 1984;White et al, 1984;Minshull et al, 1988). These data suggest that beneath fracture zone troughs the crust is often thinner, velocities are lower, and ocean layer 3 velocities (6.8 to 7.1 km/s) are uncommon.…”