  The fatigue fracture surfaces of a metallic alloy, and the stress corrosion
fracture surfaces of glass are investigated as a function of crack velocity. It
is shown that in both cases, there are two fracture regimes, which have a well
defined self-affine signature. At high enough length scales, the universal
roughness index 0.78 is recovered. At smaller length scales, the roughness
exponent is close to 0.50. The crossover length $\xi_c$ separating these two
regimes strongly depends on the material, and exhibits a power-law decrease
with the measured crack velocity $\xi_c \propto v^{-\phi}$, with $\phi \simeq
1$. The exponents $\nu$ and $\beta$ characterising the dependence of $\xi_c$
and $v$ upon the pulling force are shown to be close to $\nu \simeq 2$ and
$\beta \simeq 2$.
