  Aims. We developed a six-part collisional evolution model of the main
asteroid belt (MB) and used it to study the contribution of the different
regions of the MB to the near-earth asteroids (NEAs). Methods. We built a
statistical code called ACDC that simulates the collisional evolution of the MB
split into six regions (namely Inner, Middle, Pristine, Outer, Cybele and
High-Inclination belts) according to the positions of the major resonances
present there ($\nu_{6}$, 3:1J, 5:2J, 7:3J and 2:1J). We consider the Yarkovsky
effect and the mentioned resonances as the main mechanism that removes
asteroids from the different regions of the MB and delivers them to the NEA
region. We calculated the evolution of the NEAs coming from the different
source regions by considering the bodies delivered by the resonances and mean
dynamical timescales in the NEA population. Results. Our model is in agreement
with the major observational constraints associated with the MB, such as the
size distributions of the different regions of the MB and the number of large
asteroid families. It is also able to reproduce the observed NEAs with H < 16
and agrees with recent estimations for H < 20, but deviates for smaller sizes.
We find that most sources make a significant contribution to the NEAs; however
the Inner and Middle belts stand out as the most important source of NEAs
followed by the Outer belt. The contributions of the Pristine and Cybele
regions are minor. The High-Inclination belt is the source of only a fraction
of the actual observed NEAs with high inclination, as there are dynamical
processes in that region that enable asteroids to increase and decrease their
inclinations.
