PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

KINEMATICS MOTION OF WESTERN PART OF SULAWESI REGION
AS DERIVED BY GPS RESULTS

D.A. Sarsito ⁽¹⁾, H.Z. Abidin ⁽¹⁾, H. Andreas⁽¹⁾,
W. Triyoso⁽²⁾, and M.I.T. Taib⁽³⁾

Institute Technology Bandung, Indonesia

⁽¹⁾ Geodesy Research Division, Faculty of Civil and Environmental Engineering,
⁽²⁾ Geophysical Research Division, Faculty of Earth Sciences and Mineral Technology
⁽³⁾ Geophysical Engineering Research Division, Faculty of Earth Sciences and Mineral Technology

e-mail : dsarsito@gd.itb.ac.id
ABSTRACT

The island of Sulawesi is located at the triple juction of the Indo-Australian, Pacific and Eurasion Plates. This triple junction generated a complicated configuration of active plate boundaries with rapid micro- block rotations character. Moreover, since the relative motions of the involved plates are rapid, the area displays a lot of seismicity. Hence the problem of a better understanding of the seismotectonics of the main active structures of the area is of first importance. A dense GPS network was measured yearly since 1997 until 2006. The aim of the current study is to better define the present-day kinematics of western part of Sulawesi and to monitor the Palu-Koro fault to understand finely the interseismic behaviour.

In order to explore these problems, we try to use several GPS mapping approaches (global, regional or sub-regional) to recognize the true tectonic motion in ITRF-2005 and try to model the GPS velocities as resulting from combination of rigid block rotations and elastic deformation linked with the interseismic loading on faults. The best GPS approach is chosen base on the most realistic quality of the coordinate repeatibilities and velocities. For relatively small area, the regional and sub-regional approaches gave the best results since the global approach gave more error propagation effects that make the true deformation signal become not clear. And from these strategy, we invers the results including earthquake slip vector in the Euler vector describing the blocks motions, the faults locations, velocities and the locking depth. Four blocks of motion are used to define the area of investigation based on the geological a priori information. The results shows the North-Sula block rotate clockwise to accommodate the motion of Palu-Koro . The Palu-Koro Fault zone accomodate 42 mm/yr and shows a transtensive behaviour more complex than commonly describe, where this area also have monitored by several GPS continuous stations. And the Makassar block show an individualized anticlockwise motion with respect to Sunda Block, and come finally deaden in Borneo, where smaller deformation is inferred. All these results are usefully for better understanding of kinematics motion the area of investigation.

Key word : Sulawesi, GPS