Spin-allowed production of O(D-1) in the near-UV photolysis of ozone is studied using ab initio potential energy surfaces and quantum mechanics. The O(D-1) quantum yield, reconstructed from the absolute cross sections for eight initial vibrational states in the ground electronic state, is shown to agree with the measurements in a broad range of photolysis wavelengths and temperatures. Relative contributions of one- and two-quantum stretching and bending initial excitations are quantified, with the contribution of the antisymmetric stretch being dominant for lambda < 330 nm. Large scale structures in the low-resolution quantum yield are shown to reflect excitations in the high-frequency short bond stretch in the upper electronic state. Spin-forbidden contribution to the O(D-1) quantum yield at wavelengths lambda > 320 nm is estimated using ab initio energies of the triplet states and their spin-orbit couplings.