Sandbox models commonly produce slope failures and mass- Transport on the top free surface, which can be an analogue for submarine slides. We have been conducting shortening experiments to model accretionary wedges at subduction margins under several basement configurations of the subducting plate. Slope failures periodically occur when thrust faults reach the top surface of the models. These failures are triggered by steepening of slopes related to the displacement along the underlying thrusts. Internal stress field and physical property of materials may have little impact on the pattern and geometry of failures. Experiments with a topographic relief (e.g., horst) in the basement produce irregular distribution in time of thrusting. Long-lived thrusts, generally initiate at the foot of topographic highs, tend to form longer slopes with thick piles of failed sediments in the footwall. These suggest that anomalous amount of failed sediments in accretionary wedge regions can be used to assume topographic relief in the basement that affected the geometry of detachment. When subducted, such detachment geometries may not be easy to recognize with geophysical technique.