Answer:
 It is the planar zone of seismicity increasing with depth with increased distance from the trench. 
Step-by-step explanation:
Wadati - Benioff zone -
The planar zone of the seismicity corresponding to the down - going slab in the subduction region . 
The term was given by Hugo Benioff and Kiyoo Wadati , hence is named after these two seismologists .
It is the planar zone of the seismicity increasing with depth with the increased distance from the trench .