Variation in lithospheric stress along ridge‐transform plate boundaries

Abstract

Three‐dimensional numerical models of asthenospheric flow and deformation in the oceanic lithosphere predict variability in the stress field that reflects the geometry of the ridge‐transform boundary. A series of 3‐D Boundary Element calculations shows how spreading rate, transform offset and segment length each influence the flow and stress fields that develop during plate‐driven asthenospheric flow beneath a ridge‐transform boundary. The predicted patterns of stress‐supported seafloor relief generally follow those observed: median valleys are predicted at slow‐spreading ridges vs no rift valley or, in some cases, a small axial high at fast spreading ridges; nodal deeps occur at ridge‐transform intersections for offsets greater than 25 km; longer segments have more along‐axis deepening than short segments which do not shoal much in their center. The predicted amplitude of the stress supported topography is up to 20% (across axis) and 40% (along axis) of that observed for an assumed asthenospheric viscosity of 5×1019 Pa s and a weak lithosphere (local compensation).