We present a probabilistic seismic risk analysis of the 2006 Basel Enhanced Geothermal System (EGS) experiment. We combine induced seismicity time-dependent hazard with the RISK-UE macroseismic method and propose a logic tree approach to capture epistemic uncertainties. We find that the expected losses vary over several orders of magnitude for the tested parameters. It indicates that the previous Basel EGS seismic risk study (SERIANEX), which did not include epistemic uncertainties, led to subjective estimates. We address the issue of decision-making under uncertainty by discussing the role of model ambiguity in a simple traffic light system for EGS seismic risk mitigation. (C) 2014 Elsevier Ltd. All rights reserved.