In earthquake science, a section of an active fault that has not ruptured in a major earthquake for an unusually long time is called a seismic gap.
The concept is based on the idea that some fault segments release tectonic strain repeatedly while neighboring segments remain quiet. A quiet segment may therefore attract scientific attention because stress could be accumulating there. Researchers compare historical earthquake catalogs, geodetic measurements, GPS observations, and paleoseismic evidence when evaluating such areas.
A seismic gap is not a guaranteed earthquake prediction. Fault behavior is complex, records may be incomplete, and a quiet segment can remain quiet longer than expected or rupture together with adjacent segments. The term describes an observation and a possible risk indicator, not a timetable.
Seismic gaps are especially discussed along subduction zones and major strike-slip faults. They should not be confused with aftershock zones, which are areas where smaller earthquakes follow a mainshock, or with a seismic quiet zone, which can have a different meaning in earthquake research.