Plate convergence measured by GPS across the Sundaland/ Philippine sea plate deformed boundary: the Philippines and eastern Indonesia

The western boundary of the Philippine Sea (PH) Plate in the Philippines an d eastern Indonesia corresponds to a wide deformation zone that includes th e stretched continental margin of Sundaland, the Philippine Mobile Belt (PM B), extending from Luzon to the Molucca Sea, and a mosaic of continental bl ocks around the PH/Australia/Sunda triple junction. The GPS GEODYSSEA data are used to decipher the present kinematics of this complex area. In the Ph ilippines, the overall scheme is quite simple: two opposing rotations on ei ther side of the left-lateral Philippine Fault, clockwise to the southwest and counterclockwise to the northeast, transfer 55 per cent of the PH/Sunda land convergence from the Manila Trench to the northwest to the Philippine Trench to the southeast. Further south, 80 per cent of the PH/Sunda converg ence is absorbed in the double subduction system of the Molucca Sea and les s than 20 per cent along both continental margins of northern Borneo. Final ly, within the triple junction area between the Sundaland, PH and Australia plates, from Sulawesi to Irian Jaya, preferential subduction of the Celebe s Sea induces clockwise rotation of the Sulu block, which is escaping towar d the diminishing Celebes Sea oceanic space from the eastward-advancing PH Plate. To the south, we identify an undeformed Banda block that rotates cou nterclockwise with respect to Australia and clockwise with respect to Sunda land. The kinematics of this block can be defined and enable us to compute the rates of southward subduction of the Banda block within the Flores Tren ch and of eastward convergence of the Makassar Straits with the Banda block . The analysis made in this paper confirms that this deformation is compati ble with the eastward motion of Sundaland with respect to Eurasia determine d by the GEODYSSEA programme but is not compatible with the assumption that Sundaland belongs to Eurasia, as was often assumed prior to this study.