Wadati–Benioff zone

Diagram of Wadati-Benioff zone, from the United States Geological Survey

Seismicity cross-section, Kuril Islands subduction zone, 15 November 2006, 8.3 M_w event marked as star

A Wadati–Benioff zone (also Benioff–Wadati zone or Benioff zone or Benioff seismic zone) is a deep active seismic area in a subduction zone.^[1] Differential motion along the zone produces deep-seated earthquakes, the foci of which may be as deep as about 670 kilometres (420 mi). The term was named for the two seismologists, Hugo Benioff of the California Institute of Technology, and Kiyoo Wadati of the Japan Meteorological Agency who independently discovered the zones.^[2]

The Benioff zone earthquakes develop beneath volcanic island arcs and continental margins above active subduction zones.^[3] They can be produced by slip along the subduction thrust fault or slip on faults within the downgoing plate, as a result of bending and extension as the plate is pulled into the mantle.^[4] The deep earthquakes along the zone allow seismologists to map the three-dimensional surface of a subducting slab of oceanic crust and mantle. The angle of dip of the zone is the same as that of the subducting slab.

Along the Tonga Trench in the south Pacific the zone of earthquakes dip beneath the islands at an angle near 45 degrees down to a depth of focus of 600 kilometers. In one instance along Japan's largest island of Honshu, a Wadati–Benioff zone is characterized by two well-defined lines of earthquake foci, with the distance between each line several tens of kilometers apart.^[5]

See also

• Subduction

References