Monitoring of the Palu‐Koro Fault (Sulawesi) by GPS

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Abstract
5 years of GPS measurements across the Palu‐Koro fault (Sulawesi, Indonesia) state left lateral strike‐slip (3.4 cm/yr) with a small normal component (0.4 cm/yr). The measurements on intermediate points of the transect show that the fault is locked, at a depth estimated around 8–16 km by a very simple model. The best measured baseline linking the two most separate sites (Watatu and Toboli) shows very interestingly a constant rate of 2.6 cm/yr from 1992 to 1995, and an increased rate of 6.3 cm/yr since then. This increase is due to an earthquake on January 1, 1996 in the Minahasa trench, presumably affecting station Toboli's position by 2 cm of co‐seismic and 2 cm of post‐seismic displacement, which is added to its long term velocity. We interpret this phenomenon as additional stress loading on the Palu fault, driven by the slip during the earthquake 100 km to the North‐East.