What is the name for the inclined earthquake zone marking a descending tectonic plate?

The inclined earthquake zone marking a descending tectonic plate is called a Wadati–Benioff zone.

It forms at a subduction zone, where one lithospheric plate bends and sinks beneath another. Earthquakes occur along the descending slab and can range from shallow events near the trench to deep events hundreds of kilometres below the surface. Their sloping pattern lets scientists trace the plate as it enters the mantle.

The zone is named after Japanese seismologist Kiyoo Wadati and American seismologist Hugo Benioff. Their work helped establish that earthquakes were not confined to a thin layer near Earth’s surface.

A Wadati–Benioff zone commonly lies beneath a volcanic arc and a deep ocean trench. Not every earthquake near a plate boundary belongs to one; transform faults and continental collision zones have different geometries. The term describes the seismic pattern associated specifically with a sinking slab.