The seismic hazard analyses are considered the best methods to estimate seismic inputs, since they identify and combine, in both mathematical and physical ways, many uncertainties involved in a seismic event. They account for the seismic-geological context and historical earthquakes through seismogenic zones and attenuation equations. The analyses can be developed in probabilistic or deterministic ways, providing several scenarios. The former provides the most likely earthquake, whereas the latter provides the worst-case earthquake.