Diffuse oceanic plate boundaries: Kinematic observations and rheological constraints

Abstract

We use a thin viscous sheet model to interpret the observed shortening along a seismic reflection profile collected on the Phedre cruise (on the deforming oceanic lithosphere in the central Indian Ocean). We determine the 95% confidence region of the 1/e fall-off distance of strain rate to be between 7.1° and 20.4°, the vertically averaged power-law exponent to be between 1.6 and 18.5, and the ratio of the strength of the upper lithosphere to the lower lithosphere to be between 1 and 5.5. We calculate a simplified strength envelope of a two layered oceanic lithosphere based on the lower lithosphere deforming in accordance with the Dorn equation. This model estimates a range of between 0.2 and 20 TN m-1 for the strength of the oceanic lithosphere. The ratio of the strength of the upper lithosphere with respect to the lower lithosphere ranges between 8.6 and 13.98.