A FAULT MODEL FOR THE 1989 KILAUEA SOUTH FLANK EARTHQUAKE FROM LEVELING AND SEISMIC DATA

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.