Faulting in the South Flank of Kilauea Volcano, Hawai'i

Models developed to explain the deformation of Kilauea volcano largely rely on seismic and geodetic data that cover only a short period of activity. K ilauea's active South Flank contains two normal fault systems - the Koa'c a nd Hilina systems that must reflect longer-term deformation of the edifice. The scale and origin of these faults is poorly understood. Both fault syst ems consist of en echelon fault segments that have significant interaction and linkage. The presence of relay ramps between fault segments, systematic stepping senses, and slip and displacement data all suggest that the fault systems link down to individual larger faults. The Hilina Fault System (HF S) is greater than or equal to 42 km long and similar to9 km deep, while th e Koa'c Fault System (KFS) is underlain by two to three smaller faults, the largest of which is at least 14 km long and 4 km deep (and possibly extend s down to the basal thrust at 9 km depth). We suggest that the HFS has deve loped as a result of 'differential slip' on the thrust at the base of the e difice and that footwall uplift on the HFS causes antithetic faulting in th e South Flank, which provides a new explanation of the origin of the KFS. ( C) 2001 Elsevier Science B.V. All rights reserved.