Global Evidence for Off‐Axis Flexural Modification of Abyssal Hill Faults at Mid‐Ocean Ridges

Abstract

Young oceanic lithosphere flexes as axial topography decays across mid‐ocean ridge shoulders, yet this deformation has been quantified at only a few segments, leaving its global expression poorly constrained. We analyzed 50 across‐axis bathymetric profiles from 21 regions spanning slow to fast spreading rates, identified 1,201 abyssal‐hill‐bounding fault scarps, and measured the change in apparent tectonic strain across the ridge shoulder from cumulative heave. After correcting for apparent‐throw reduction by surface process, three regimes emerge: (a) Axial‐valley ridges record shortening that increases with axial relief, (b) Fast‐spreading axial‐high ridges record extension that increases with relief, (c) Axial‐high ridges at slow‐to‐intermediate spreading rates record negligible flexural strain, because their thicker axial lithosphere acquires little accretional curvature. A simple flexural model with strain proportional to axial relief reproduces these patterns to first order. Flexure, set by axial relief and axial lithospheric thickness, systematically modifies fault‐generated seafloor morphology at divergent plate boundaries.