The seismic hazard (or seismic hazard) of a region is the probability that seismic movements of a certain importance will occur in it within a certain period of time. This concept should not be confused with seismic risk, which depends on anthropogenic factors and refers to potential damage.

Seismic hazard is a geophysical magnitude that gives the probability of occurrence of earthquakes in a specific geographic area during a given time interval and involving ground accelerations above a certain given value. It therefore gives an idea of ​​the probability of certain ground accelerations occurring. Since the terms seismic hazard and seismic risk are often confused, it is necessary to indicate that this refers to the probability of occurrence of losses or damages caused by earthquakes (involves anthropogenic variables). While the seismic hazard is higher on the coast of Alaska than on the coast of Algeria, the risk is greater on the latter due to the greater population density.

Seismic hazard estimates are frequently based on statistical analysis of the seismic history (catalog) of the area of ​​interest. A common empirical formula for the probability of occurrence of some intensity earthquakes in a period is:

Where:.

Admitting that the occurrence of earthquakes is governed by a Poisson process, the probability that in period T k earthquakes of intensity greater than a certain threshold would occur would be:

Therefore the probability of occurrence of an earthquake would be given by:.

This last formula numerically coincides with the empirical formula ().

The seismic danger, referring to the occurrence of earthquakes in a region, can be represented by maps. These maps are representation instruments prepared from the study of the following factors of the region: historical record of earthquakes, location of faults, etc.