A characteristic earthquake is a repeating, large earthquake that occurs more frequently than local seismic monitoring would suggest.[1] Characteristic earthquakes are usually defined from paleoseismology observations.
This has important implications for seismic hazard calculations (and earthquake insurance rates). Basically, it implies that there is a section of a fault that has very little observed seismicity, but is a high hazard because the paleoseismic studies show a regular pattern of large earthquakes.