GEOLOGY

Detailed explanation-1: -A deep-focus earthquake in seismology (also called a plutonic earthquake) is an earthquake with a hypocenter depth exceeding 300 km. They occur almost exclusively at convergent boundaries in association with subducted oceanic lithosphere.

Detailed explanation-2: -The deepest earthquakes occur within the core of subducting slabs-oceanic plates that descend into the Earth’s mantle from convergent plate boundaries, where a dense oceanic plate collides with a less dense continental plate and the former sinks beneath the latter.

Detailed explanation-3: -Answer and Explanation: Deep-focus earthquakes are associated with subduction zones where oceanic crust subducts beneath less dense continental crust.

Detailed explanation-4: -Deep-focus earthquakes are concentrated in subduction zones because while one plate is subducting it creates earthquakes which make deep-focus earthquakes.

Detailed explanation-5: -Over 80 per cent of large earthquakes occur around the edges of the Pacific Ocean, an area known as the ‘Ring of Fire’; this where the Pacific plate is being subducted beneath the surrounding plates. The Ring of Fire is the most seismically and volcanically active zone in the world.