Which plate boundary type is associated with subduction and megathrust earthquakes?

• A. Divergent boundaries
• B. Transform boundaries
• C. Convergent boundaries (subduction zones)
• D. No boundaries

Answer: (C)

Megathrust earthquakes occur where big slabs of crust are being forced to dive beneath another plate—subduction. That happens at convergent boundaries known as subduction zones. The interface between the colliding plates gets stuck as they push, so enormous amounts of stress build up along a very long fault. When that stress finally releases, a massive slip occurs on the megathrust fault, producing a huge earthquake and often a tsunami.

Other boundary types don’t produce these megathrust ruptures: divergent boundaries involve plates moving apart and tend to produce smaller normal-fault quakes, while transform boundaries involve side-by-side sliding with strike-slip motion. So the plate boundary type that fits subduction and megathrust earthquakes is convergent boundaries at subduction zones.