Defining the plate boundaries in the Azores region

The Azores Archipelago occupies the boundary zone where three major tectonic plates (Eurasia, Nubia, and North America) meet to form the Azores Triple Junction. Repeat observations from six campaigns carried out between 1993 and 2001 for the TANGO network of GPS sites now allow reliable estimations of the current motions of the involved plates at millimeter-scale resolution. Analysis of these space-geodetic data demonstrates that, during the observation period, Santa Maria Island followed the average Nubian plate movement and Graciosa Island mimicked the average Eurasian plate behavior. All other GPS sites display intermediate behavior, consistent with their locations within the active inter-plate deformation area. The active deformation area is well modeled by an elastic half-space approach, with the segmentation of the Eurasian–Nubian plate boundary constrained by other geophysical data.