Tectonic and geomorphological evolution of forearcs during ridge subduction

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Subduction of submarine ridges causes considerable uplift and deformation of the upper plate and may lead offshore to the indentation of the forearc and onshore to the development of distinct patterns of faulting, the formation of marine terraces and the deflection of rivers above the subducting ridge. Depending on the orientation of the ridge relative to the plate convergence direction, the ridge may either be stationary or migrate along the margin, causing a wave of forearc uplift and subsequent subsidence. Here we propose to use 3D numerical models to investigate the tectonic and topographic evolution of forearcs affected by ridge subduction. Using different model setups we will distinguish between accretive/erosive margins and migrating/non-migrating ridges, respectively. We will vary the ridge shape and the mechanical strength of the forearc and the plate interface to identify the most influential parameters. The results will be analysed with respect to the ridge-induced changes of the forearc geometry, displacement and stress field. To investigate the impact of ridge subduction on the geomorphological evolution of the forearc, the tectonic models will be coupled to a landscape evolution model. The modelled landscapes will reveal if a subducting ridge may lead onshore to the deflection of rivers near the coast. We will compare our findings with the collision zones of the Nazca Ridge (migrating along the erosive Peruvian margin), the Cocos Ridge (subducting stationary beneath the erosive Central American margin) and the Gagua Ridge (migrating along the accretive Ryukyu island arc).