Wadati-Benioff zone

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A profile through the Kuril Trench is the Wadati-Benioff zone of the trench , in which earthquake hypocenters occur at great depths, which lie along the tectonic plate subducted here at an angle of around 45 °. The star above marks the hypocenter of the earthquake on November 15, 2006.

Wadati-Benioff zones (mostly called Benioff zones in the older literature ) are formed by the plunging plate during a subduction . They are characterized by ever deeper hypocenters of earthquakes . The discovery of these zones was another clue for the theory of plate tectonics . They were discovered independently of one another by the US seismologist Hugo Benioff and his Japanese colleague Kiyoo Wadati and later named after them.

In the Wadati-Benioff zones, earthquake foci are detected up to a depth of 700 km, the foci being arranged on an inclined surface. The earthquake foci trace the position of the subducted tectonic plate sinking into the earth's mantle . In contrast to the upper mantle, the relatively cool material of the descending plate retains its ability for a long time to relieve the stresses in the rock caused by subduction through brittle fracture , which is evident every time in an earthquake event.

Another feature of the Wadati-Benioff zones is the geothermal depth anomaly . Due to the slowly warming rock of the subducted plate, the temperatures are lower than would be expected for these depths due to the proximity to the earth's mantle.

Wadati-Benioff zones occur wherever subduction zones are formed, next to the Kuril Trench shown, for example on the west coast of America and around the Pacific. The earthquake zones are there according to the subduction direction - the oceanic crust of the Pacific Ocean is the sub-plate and is subducted - inclined from the ocean to the continent or dive under an island arc.

Individual evidence

  1. Graphics ( memento of August 14, 2009 in the Internet Archive ) on the earthquake on the Kuril Islands of November 15, 2006 on the USGS website
  2. ^ Jean-Pierre Burg: Large-scale structures and plate tectonics. Teaching material from the Structural Geology and Tectonics group, ETH Zurich ( Memento from February 1, 2012 in the Internet Archive ) (PDF; 1.5 MB)

Web links