Crustal motion in Indonesia from Global Positioning System measurements

[1] We present the crustal motion velocity field for the Indonesian archipelago based on Global Positioning System (GPS) field surveys conducted from 1991 to 1997, and 2001, totaling more than 150 sites, as well as on a reanalysis of global tracking data in the Scripps Orbit and Permanent Array Center archive from 1991 to 2001 in International Terrestrial Reference Frame 2000. We compute poles of rotation for the Australia, Eurasia, and Pacific plates based on our analysis of the global GPS data. We find that regional tectonics is dominated by the interaction of four discrete, rotating blocks spanning significant areas of the Sunda Shelf, the South Banda arc, the Bird's Head region of New Guinea, and East Sulawesi. The largest, the Sunda Shelf block (SSH), is estimated to be moving 6 +/- 3 mm/yr SE relative to Eurasia. The South Banda block (SBB) rotates clockwise relative to both the SSH and Australia plate, resulting in 15 +/- 8 mm/yr of motion across the Timor trough and 60 +/- 3 mm/yr of shortening across the Flores Sea. Southern New Guinea forms part of the Australia plate from which the Bird's Head block (BHB) moves rapidly WSW, subducting beneath the Seram trough. The East Sulawesi block rotates clockwise about a nearby axis with respect to the Sunda Shelf, thereby transferring east-west shortening between the Pacific and Eurasia plates into north-south shortening across the North Sulawesi trench. Except for the Sunda Shelf, the crustal blocks are all experiencing significant internal deformation. In this respect, crustal motion in those regions does not fit the microplate tectonics model.