Mechanical control of oceanic plate boundary geometry

We present a global analysis of oceanic plate boundary geometry based on th e mechanics of relative plate motion at mid-ocean ridges and transform faul ts. If the observed geometry formed by the first-order segmentation of ocea nic plate boundaries represents a state of mechanical equilibrium, we find the relative strength of spreading ridges, and their bounding transform fau lts to be fundamental to its organisation. A consideration of power dissipa tion along adjacent lengths of spreading ridge and transform fault leads to a simple relationship between spreading obliquity and relative strength. I ncreased spreading rate is found to decrease the strength of spreading segm ents relative to transform faults. Proximity to an active hotspot reduces t he relative strength of spreading ridges. (C) 1999 Elsevier Science B.V. Al l rights reserved.