Mechanical role of backstops in the growth of forearcs

摘要: We use numerical and laboratory modeling to analyze the mechanical role of backstops in overriding plate at subduction zones. A backstop is defined as a region within forearc that has significantly greater shear strength than sediment lying farther trenchward; it can be thought bulldozer behind an accretionary wedge. calculate stress displacement fields forearcs for various models using finite element method, we simulate deformation over small-scale model. In this way model effects properties geometry on structures. find growth outer arc high, development inner belt with landward vergence, seemingly paradoxical presence undeformed basin otherwise highly deformed explained by assuming existence geometrically simple geologically reasonable contrasts compared sediments just trenchward it. The structures produced our are quite insensitive rheology, boundary conditions, exact mesh employed. general types observed depend only weakly upon backstop. These results suggest detailed picture underlying cannot determined from surface information alone. Backstops which contact wedge dips arcward rather trenchward, however, should produce slightly different structures, less both high landward-vergent belt. Although natural far more complex models, they exhibit many same features, indicating relatively mechanics may very important factor overall forearcs.