Seismic gaps refer to sections of plate boundaries that have not experienced significant earthquake activity in the recent past. Option 1 is incorrect because seismic gaps are not specifically related to tsunamis but rather to earthquake activity. Option 2 is incorrect because seismic gaps are characterized by a lack of earthquake activity, rather than repeated rupturing. Option 4 is not directly related to seismic gaps as volcanic activity and seismic activity can occur independently at plate boundaries. The correct answer, option 3, highlights that seismic gaps are sections of plate boundaries that have not ruptured in the recent past, indicating that these areas may be at higher risk of experiencing future earthquakes.