Changes

Oceanic [[crust]] generated in MOR will migrate nearer to the trench. Driving mechanism which influences the dynamics of subduction zone is density. Oceanic crust is denser than continental one, therefore the sinking of oceanic crust below continental crust is possible. Forces driving subduction are ridge-push and slab-pull. As oceanic crust moves away from the ridge, conductive cooling turns the crust to be denser. Density of oceanic crust varies laterally, increasing from the ridge axis to the trench. Such force is parallel to the plate since it pushes in topographic slope. Slab-pull force involves cold, dense oceanic lithosphere and hot, lighter [[mantle]]. Slab-pull force dominantly accommodates the vertical displacement of plate. This provides the biggest force for oceanic crust to sink.

Oceanic [[crust]] generated in MOR will migrate nearer to the trench. Driving mechanism which influences the dynamics of subduction zone is density. Oceanic crust is denser than continental one, therefore the sinking of oceanic crust below continental crust is possible. Forces driving subduction are ridge-push and slab-pull. As oceanic crust moves away from the ridge, conductive cooling turns the crust to be denser. Density of oceanic crust varies laterally, increasing from the ridge axis to the trench. Such force is parallel to the plate since it pushes in topographic slope. Slab-pull force involves cold, dense oceanic lithosphere and hot, lighter [[mantle]]. Slab-pull force dominantly accommodates the vertical displacement of plate. This provides the biggest force for oceanic crust to sink.

Resistive forces are also present in convergent plate boundary. As oceanic crust moves laterally, the base of the plate produces shear resistance, causing deformation of mantle wedge. The contact between oceanic and continental crust along fault plane creates frictional force. On the other hand, when subducted slab enters the depth of 670 km, resistance to penetration occurs because facing discontinuity.

Resistive forces are also present in convergent plate boundary. As oceanic crust moves laterally, the base of the plate produces shear resistance, causing [[deformation]] of mantle wedge. The contact between oceanic and continental crust along fault plane creates frictional force. On the other hand, when subducted slab enters the depth of 670 km, resistance to penetration occurs because facing discontinuity.

===Zonation of Deformation===

===Zonation of Deformation===

Subduction produces areas of different deformation mechanism. Different mechanisms lead to different potential of earthquake. Keary and Vine<ref name=KV /> constructs [[cross-section]] of subduction zone consisting three zonations of deformation: a, b, and c. This classification is based on deformation mechanism and materials involved.

Subduction produces areas of different [[deformation]] mechanism. Different mechanisms lead to different potential of earthquake. Keary and Vine<ref name=KV /> constructs [[cross-section]] of subduction zone consisting three zonations of deformation: a, b, and c. This classification is based on deformation mechanism and materials involved.

Zone ‘a’ represents plastic deformation of oceanic crust plunging into the trench. Flexural bending of oceanic crust creates topographic bulge, causing regional positive gravity anomaly of +500 gu. Zone ‘b’ is the contact of oceanic and continental crust. Compressive forces are built in the overriding crust and extensional regime develops landward on continental crust. As the plate descending to zone ‘c’, the interaction with asthenosphere produces deformation due to unbending of the slab. This mechanism leads to internal deformation of oceanic crust.

Zone ‘a’ represents plastic deformation of oceanic crust plunging into the trench. Flexural bending of oceanic crust creates topographic bulge, causing regional positive gravity anomaly of +500 gu. Zone ‘b’ is the contact of oceanic and continental crust. Compressive forces are built in the overriding crust and extensional regime develops landward on continental crust. As the plate descending to zone ‘c’, the interaction with asthenosphere produces deformation due to unbending of the slab. This mechanism leads to internal deformation of oceanic crust.

Accretionary prism has imbricate listric thrust dipping towards the arc. As subduction progresses, the listric fault has increasing dip and rotation towards the arc. An good analogy of accretionary prism formation is sand crushed by a bulldozer. Sand accumulation will experience “compression” from bulldozer, forming sand wedge as the bulldozer moving. Sand wedge will increase in dip until it reaches its angle of repose.

Accretionary prism has imbricate listric thrust dipping towards the arc. As subduction progresses, the listric fault has increasing dip and rotation towards the arc. An good analogy of accretionary prism formation is sand crushed by a bulldozer. Sand accumulation will experience “compression” from bulldozer, forming sand wedge as the bulldozer moving. Sand wedge will increase in dip until it reaches its angle of repose.

Imbricate listric thrust also implies to the order of age. Older sediments and metamorphic rocks certainly have experienced more intensive deformation than the younger ones. As a consequence, the older part must have existed in structural high. This transportation enables the discovery of old sediments and metamorphic rocks on the uppermost part of accretionary prism.

Imbricate listric thrust also implies to the order of age. Older sediments and metamorphic rocks certainly have experienced more intensive [[deformation]] than the younger ones. As a consequence, the older part must have existed in structural high. This transportation enables the discovery of old sediments and metamorphic rocks on the uppermost part of accretionary prism.

===Subduction-related Basins===

===Subduction-related Basins===