Modeling interactions between plate-boundary forces and evolving
resistance at mid-ocean ridges as the origin of non-uniform seafloor
growth
Abstract
Evidence for asymmetric plate growth, variable crustal thickness, and
non-uniform spreading rates is ubiquitous on the seafloor. However,
conventional numerical modeling approaches are often incapable of
explaining the non-uniform growth of oceanic lithosphere. Noting that
plate-boundary forces can dynamically determine plate speed by finding a
balance against the resistance to extension at ridge axes, we introduce
plate-boundary tractions instead of kinematics to drive plate motions in
numerical models for mid-ocean ridges. We construct such models using
FLAC, an open-source finite element code for geodynamic simulations. Our
preliminary two-dimensional models for slow-spreading ridges have
constant tractions on the boundary far from the ridge. Applying periodic
variations in thermal states or magmatic accretion rates at the
spreading center, we monitor how plate speed, crustal thickness,
faulting styles and fault offset change in time. We also compare the
model results to the temporal variations found in the bathymetry and
seismic reflection data along a 1500 km-long transect across the
slow-spreading South Atlantic seafloor, which were acquired in the 2017
CREST (Crustal Reflectivity Experiment Southern Transect) expedition.