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Department of Geology
One Shields Avenue
University of
CaliforniaDavis
Davis, California 95616
(E.C.C.)
Department of Earth and Planetary Science
307 McCone
Hall
University of CaliforniaBerkeley
Berkeley, California
94720-4767
burgmann{at}seismo.berkeley.edu
(R.B.)
University of Southern California
Earth Sciences
Los
Angeles, California
90089-0740
owen{at}earth.usc.edu
(S.E.O.)
The Hilina fault system is a set of normal faults that accommodate
extension of the mobile south flank of Kilauea Volcano. Large earthquakes
(M
6) and aseismic fault slip transport the flank southeastward
along a basal detachment at
810 km depth. Both the 1975 M
7.2 Kalapana and the 1868 M 7.9 Great Kau earthquakes produced slip
on the Hilina faults. We compare Kalapana earthquake fault offsets, ground
displacements derived from analysis of geodetic surveys, and model
displacements from a dislocation model to evaluate whether the central Hilina
fault slip associated with the Kalapana earthquake was due to (1) shallow
normal faulting independent of basal detachment slip or (2) deep normal
faulting directly linked to basal detachment slip. Our analysis shows that
observed site motions at the coast are significantly greater than model
displacements expected from a dislocation model of basal detachment slip
alone. To explain ground displacements and fault offsets, we require fault
slip on shallow normal faults (as deep as 23 km) triggered by slip on
the basal detachment. Leveling data along the Chain of Craters Road and
vertical fault offsets across the central Hilina fault system suggest that the
Kalapana earthquake produced block rotation of the hanging-wall blocks.
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