The Benioff zone is a zone of seismic activity that occurs along the subducting slab of an oceanic plate as it descends into the mantle beneath an overriding plate. This zone is characterized by a dipping plane of earthquakes, which can extend from near the surface to depths of 700 kilometers. The study of Benioff zones provides critical insights into the mechanics of subduction and the forces driving plate tectonics.
Reference: Isacks, B., Oliver, J., & Sykes, L. R. (1968). “Seismology and the New Global Tectonics.” Journal of Geophysical Research, 73(18), 5855-5899.