We use burst vibrothermography to characterize, i.e., to determine the dimensions and location of buried vertical cracks of rectangular shape. Surface breaking as well as buried cracks are investigated. We calculate the surface temperature distribution generated by a rectangular vertical crack when excited by an ultrasound burst of constant power. By fitting synthetic data with added white noise, we analyze the effect of the burst duration on the accuracy of the retrieved dimensions and depth of the crack. We take data on samples containing artificial calibrated vertical cracks. The results of the fittings performed on these experimental data show that it is possible to characterize rectangular vertical cracks from burst vibrothermography experiments.