Methodologies available for the calculation of seismic hazards are well established. The historical method requires only a catalog of historical earthquakes, appropriate attenuation functions for ground motions in the region, and site response functions; the deductive method requires, in addition, a description of possible faults and earthquakes sources, and the parameters describing seismicity for those faults and sources. Uncertainties in interpretations can be handled explicitly through multiple hypotheses, leading to uncertainties in seismic hazard. Accounting for these uncertainties in seismic hazard computations leads to the most informed decisions for earthquake risk mitigation.