Using SAR interferometry (InSAR), the deformation field of the Mw=6.6, 1998 Aiquile, Bolivia earthquake is mapped, and
the epicentre accurately located for the first time. Elastic dislocation modelling is used to demonstrate that the measured
displacements are best explained with a ~N–S oriented fault, with a strike that is oblique to the principal topographic features in
the region, and a location that agrees with a Modified Mercalli Intensity map constructed from observations of damage in the
surrounding area. A variable-slip solution for a fault in this orientation is obtained which predicts peak slip of 1.42 m at depths
of ~4–5 km on the fault plane and has an estimated seismic moment, M0=8.441018 N m, which agrees with estimates from
long-period seismology. This is the first time that a fault has been demonstrated unambiguously to be active in the Central
Andes, and since there was no previous knowledge of an active fault with this location or orientation, a necessary conclusion is
that our understanding of seismic hazard in this region is limited.