Forearc

Due to collisional stresses as one tectonic plate subducts under another, forearc regions are sources for powerful earthquakes.

[4][5] Initial theories proposed that the oceanic trenches and magmatic arcs were the primary suppliers of the accretionary sedimentation wedges in the forearc regions.

[2] Over geological time there is constant recycling of the forearc deposits due to erosion, deformation and sedimentary subduction.

In the later stages of collision, the forearc region may be sutured, rotated and shortened which can form syn-collisional folds and thrust belts.

[2] In general, the forearc topography (specifically in the trench region) is trying to achieve an equilibrium between buoyancy and tectonic forces caused by subduction.

[2] The relationship between surface slope and subduction thrust also plays a huge role in the variation of forearc structure and deformation.

Basin depth depends on the supply of oceanic plate sediments, continentally derived clastic material and orthogonal convergence rates.

These mega thrust earthquakes may be correlated with low values of heat flow generally associated with forearc regions.

There is evidence from geothermal data and models which show the slab-mantle interface, levels of friction and the cool oceanic lithosphere at the trench.