The orthogonality of subduction: An empirical rule?

Abstract

Measurement of the angle of plate convergence (obliquity of subduction) along twenty-one trench and transform boundaries reveals that the direction of plate convergence is not randomly distributed, but rather is strongly bimodal. Plate convergence is most commonly taken up along a system of strike-slip faults and trench segments in which the direction of plate convergence is approximately normal to the trench axis (orthogonal subduction). Slip vectors measured along these trench segments confirm the observation that, in general, oceanic lithosphere is subducted nearly perpendicular to the trench axis. Plate boundaries evolve, often by forming new plate boundaries, in ways that tend to maintain this pattern of orthogonal subduction.