The geometry of the fault that ruptured during the M6.1 south flank earthquake on Kilauea volcano in 1989 is determined from leveling data. The elastic dislocation, in a homogeneous elastic half-space, that best fits the data is found using a nonlinear inversion procedure. The best fitting model is a gently dipping thrust fault that lies at 4 km depth. This is significantly shallower than the 9 km hypocentral depth determined from the local seismic network. Two-dimensional finite-element calculations indicate that at least part of this discrepancy can be attributed to the focusing of the surface deformation by the upper few kilometers of compliant, low-density lavas. We conclude that it is important to include realistic elastic structure to estimate source geometry from geodetic data. ¿ American Geophysical Union 1991