The deformation field around the southern Great Sumatran Fault (GSF) in the vicinity of the February 15 1994 Mw=6.8 Liwa earthquake has been determined by geodetic survey. Geodetic trilateration and Global Positioning System (GPS) measurements were carried out in July 1991 in the Ranau Lake-Liwa area. A second geodetic survey reoccupied the same stations in September 1994, seven months after the Liwa earthquake. Despite the limited number of benchmarks, most of the measured displacement appears to be related to the 1994 earthquake. In addition, we show that most of this co-seismic deformation is localized along a narrow zone corresponding to the GSF segment with a right lateral displacement of about 70 cm. ¿ American Geophysical Union 1996