Figure F3. Depth to axial low-velocity zone plotted against spreading rate (modified from Purdy et al., 1992; Carbotte et al., 1997b). Depth versus rate predictions from two models of Phipps Morgan and Chen (1993) are shown, extrapolated subjectively to 200 mm/y (dashed lines). Penetration to date in Holes 504B and 1256D is shown by solid vertical lines, and planned deepening for Expeditions 309 and 312 is indicated. MAR = Mid-Atlantic Ridge, EPR = East Pacific Rise, JdF = Juan de Fuca Ridge, Lau = Valu Fa Ridge in Lau Basin, CRR = Costa Rica Rift.