The position of island arc ridges relative to slab position agrees agrees well with partial melting initiated at 150 km depth. Oceanic crust has insignificant amounts of radiogenic elements. Divergent plate motion. Convergent plate motion . For example, the collision of India with Eurasia is deforming and squeezing China towards the east along successions of strike-slip faults.
Earthquakes occur in the brittle zone of the crust.
In most regions, this is in the upper 12-15 km of the crust. B. Important exceptions this predicted transition depth are areas of subduction, where geotherms are depressed into the mantle, deepening the depth the brittle-ductile transition to perhaps 50 km or more. C. A puzzle is the existence of earthquakes at depths up to 650 km in descending slabs. This is far beyond the depth of the brittle-ductile transition. D. Seismicity is the space-time distribution of earthquakes.