Nine of the ten largest earthquakes of the last 100 years were subduction zone events , which included the 1960 Great Chilean earthquake , which , at M 9.5 , was the largest earthquake ever recorded ; the 2004 Indian Ocean earthquake and tsunami ; and the 2011 Tōhoku earthquake and tsunami . The subduction of cold oceanic crust into the mantle depresses the local geothermal gradient and causes a larger portion of Earth to deform in a more brittle fashion than it would in a normal geothermal gradient setting . Because earthquakes can occur only when a rock is deforming in a brittle fashion , subduction zones can cause large earthquakes . If such a quake causes rapid deformation of the sea floor , there is potential for tsunamis , such as the earthquake caused by subduction of the Indo-Australian Plate under the Euro-Asian Plate on December 26 , 2004 that devastated the areas around the Indian Ocean . Small tremors which cause small , nondamaging tsunamis , also occur frequently
2004 Indian Ocean earthquake and tsunami
2004 Indian Ocean earthquake and tsunami
Subduction