What is the term for areas concentrated with earthquakes along subduction zones?

The term for areas concentrated with earthquakes along subduction zones is indeed Benioff zones. These zones are specific regions where the subducting oceanic plate descends into the mantle beneath a continental plate or another oceanic plate, leading to intense seismic activity. The term originates from the work of the seismologist Hugo Benioff, who studied the patterns of earthquake locations and depths associated with such subduction processes.

In Benioff zones, earthquakes can occur at varying depths, creating a sloping plane of seismicity that correlates with the angle at which the tectonic plate is subducting. This feature highlights the relationship between plate tectonics and earthquake occurrences, emphasizing how subduction is a key driver of seismic activity in certain geographic locations.

The other terms mentioned do not refer specifically to the concentration of earthquakes along subduction zones. For example, subduction zones are the broader tectonic features themselves, rift valleys relate to divergent boundaries where plates are moving away from each other, and fault lines refer generally to fractures in the Earth's crust where movement has occurred, but not necessarily linked to subduction zones specifically.