Seismic gaps are

Seismic gaps are defined as segments of active plate boundaries or fault zones that have not experienced a major earthquake or rupture for a prolonged period [3]. These areas are considered "quiet" and "overdue" for seismic activity because they are seismically locked, meaning they accumulate significant strain energy over decades or centuries [2]. Unlike creeping segments that release energy through frequent small tremors, seismic gaps represent regions where the fault is stuck, posing a high risk for future catastrophic earthquakes when the accumulated stress eventually exceeds rock strength. Seismologists use the history of earthquake frequency along plate boundaries to identify these gaps, as they form a distinct break in the earthquake occurrence record [2]. Consequently, the seismic gap hypothesis suggests that these un-ruptured sections are the most likely locations for the next large-scale seismic event [2].

Sources

1. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > Prediction > p. 30
2. [3] https://www.sciencedirect.com/science/article/pii/S0040195125001271
3. [2] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 17: Contemporary Issues > Earthquake Forecasting > p. 14