Plate coupling variation and block translation in the Andreanof segment of the Aleutian arc determined by subduction zone modeling using GPS data

We use GPS measurements in the first geodetic study of plate coupling on the Andreanof segment, Aleutian subduction zone. Convergence of 7.3 cm/yr at the subduction zone results in northwestward displacements greater than 1 cm/yr at stations located on the west end of the Andreanof region, but velocities at the east end are smaller inmagnitude and oriented west-southwest. These velocity variations are caused by differences in plate coupling along the subduction zone, which correlate with the rupture zones of the 1986 and 1996 M(w)8 earthquakes. We construct a dislocation model to estimate the velocity of the arc in the Andreanof region relative to North America, and fault plane coupling coefficients. Our best model shows a southwestward velocity of 7.8 mm/yr, a high degree of coupling in the main thrust zone at the west end of the subduction zone, and little to no coupling at the east end.