Question

12:24 1 LTE Twitter Close What causes and controls subduction zone earthquakes? extra credit slide PPTX - 169 KB Extra credit 3% 15th Annual Olan Kruse Lecture oceanic crust continental crust lithosphere earthquakes asthenosphere slow-moving currents in the mantle By Dr. Nathan Bangs, Senior Research Scientist, Institute for Geophysics, University of Texas at Austin 7:00 PM, Thursday, April 18, 2019 Peacock Auditorium, BES 100

Answer 1

The causes of earthquakes in subduction zones are the stresses that accumulate at the interface of the subducting and the overriding plates. Due to the release of stress, movements occur along a fault plane which dips at low angles to form a thrust. The movements along the thrust faults cause seismic activity which may include strong earthquakes. Thus, the seismicity in a subduction zone arises due to the gradual movement of the two plates (oceanic and continental; as shown in the diagram) which causes rupture at the plate interface resulting in earthquakes.

Subduction zone earthquakes are controlled by tectonic forces governed by:

- friction between rocks in the zone of the thrust faults

- the rate or the velocity at which the plates are moving,

- the age and length of the subducting slab,

- the dip or the angle of the thrusts,

All of such factors determine the dynamic interactions between the two plates in a subduction zone. Variations in such factors result in larger or smaller earthquakes.