Corrected displacement amplitude spectra of weak and moderate (ML=2.5--5.0) Vrancea earthquakes (h=0--201 km) exhibit an obvious shape with two corner frequencies and two slopes. This behavior is related to local inhomogeneities within the seismic zone, and a heterogeneity parameter, ϵ is defined as the fraction of the complete stress drop released during earthquake (barrier model) or the ratio of the asperity to source radii (asperity model). The parameter ϵ is evaluated as the ratio of the first comer frequency versus the second one and it ranges from 0.50 to 0.15. The heterogeneity appears to increase with increasing magnitude (ϵ decreases), suggesting that the earthquakes represent the failure of asperities. This behavior is not evident for the events in the 30--50 km depth interval. A mostly crack origin of earthquakes in this zone is suggested. This region is found to be more homogeneous and able to decouple the seismic activities in the crust and sinking slab. The depth distribution of local inhomogeneities within the region is heterogeneous. The crust and two intermediate depth intervals, 90--110 km and 120--160 km, are the most heterogeneous and have occurrence potential for moderate earthquakes. The two intermediate zones show the highest activities, which are slightly decoupled due to a more homogeneous layer (110--120 km). ¿ American Geophysical Union 1987