A kinematic model for evolution of island arc-trench systems, Geophys

Plate subduction zones are typically characterized by the patterns of surface topography and gravity anomalies consisting of island-arc high, trench low, and outer-rise gentle high. These patterns are stable on the time scale of 106-107 yr. At some subduction zones, regardless of its age, steady uplift of marine terraces formed by eustatic sea-level changes during the last lo5 yr can be also observed. The stable patterns of topography and gravity anomalies and the steady uplift of marine terraces seem to contradict each other. We constructed a kinematic model which could explain the evolution process of island arc-trench systems and demonstrated that this puzzle could be solved by considering the effect of accretion at plate boundaries. In our model the lithosphere-asthenosphere system is represented by a stratified visco-elastic half-space under gravity, which consists of a high-viscosity surface layer and a low-viscosity substratum. The rheological properties of both layers are assumed to be a Maxwell fluid in shear and an elastic solid in bulk. Interaction between oceanic and continental plates is represented by the steady increase of discontinuity in tangential displacement across the plate boundary. Th