  We present an analytical and numerical study of the orbital migration and
resonance capture of fictitious two-planet systems with masses in the
super-Earth range undergoing Type-I migration. We find that, depending on the
flare index and proximity to the central star, the average value of the period
ratio, $P_2/P_1$, between both planets may show a significant deviation with
respect to the nominal value. For planets trapped in the 2:1 commensurability,
offsets may reach values on the order of $0.1$ for orbital periods on the order
of $1$ day, while systems in the 3:2 mean-motion resonance (MMR) show much
smaller offsets for all values of the semimajor axis. These properties are in
good agreement with the observed distribution of near-resonant exoplanets,
independent of their detection method. We show that 2:1-resonant systems far
from the star, such as HD82943 and HR8799, are characterized by very small
resonant offsets, while higher values are typical of systems discovered by
Kepler with orbital periods approximately a few days. Conversely, planetary
systems in the vicinity of the 3:2 MMR show little offset with no significant
dependence on the orbital distance. In conclusion, our results indicate that
the distribution of Kepler planetary systems around the 2:1 and 3:2 MMR are
consistent with resonant configurations obtained as a consequence of a smooth
migration in a laminar flared disk, and no external forces are required to
induce the observed offset or its dependence with the commensurability or
orbital distance from the star.
