Stress calculation using Coulomb 3.4 (Toda et al, 2011). Guided by the Seismological Survey of Croatia aftershocks and the U.S. Geological Survey (USGS) mainshock ‘moment tensor’ (which gives the geometry, sense of slip, and energy release), we assume a 24-kilometer-long by 10-kilometer-wide fault dipping 76° to the southwest, with 0.6 meters of right-lateral and 0.01 meter of reverse slip, with its upper edge buried 2.6 kilometers below the surface. The diversity of aftershock focal mechanisms means our source model is likely over-simplified.