HR: 11:10h
AN: V11G-04    [PDF]
TI: Rethinking the Standard Model of Kilauea's South Flank Deformation
AU: * Cervelli, P F
EM: pcervelli@usgs.gov
AF: U.S. Geological Survey Hawaiian Volcano Observatory, P.O. Box 51, Hawaii National Park, HI 96718 United States
AU: Miklius, A
EM: asta@usgs.gov
AF: U.S. Geological Survey Hawaiian Volcano Observatory, P.O. Box 51, Hawaii National Park, HI 96718 United States
AU: Swanson, D A
EM: donswan@usgs.gov
AF: U.S. Geological Survey Hawaiian Volcano Observatory, P.O. Box 51, Hawaii National Park, HI 96718 United States
AU: Douglas, A
AF: School of Earth Sciences Victoria University of Wellington, P.O. Box 600, Wellington, 6015 New Zealand
AB: Over the last two decades, a standard model of deformation at Kilauea's south flank has emerged. Consisting of two main structures, the model includes a 9 to 10 km deep basal decollement, which slips steadily at 10 to 20 cm/yr, and a deep east rift zone, which opens at an equal rate. The two parts of the model are fundamentally interdependent in that they represent Kilauea's south flank as a large, mobile block that is, in the long run, decoupled from the rest of the island. Several recent papers have taken this model at more or less face value. Thus, the conclusions of these papers are conditional on whether or not the model is correct. Evidence is accumulating that it is not. First, a deep, rapidly opening east rift zone predicts significant subsidence within the rift zone and significant uplift on Kilauea's south flank. Continuous GPS receivers in these areas observe neither. Second, a recent pressurization of the east rift zone in early 2002 produced a deformation field inconsistent with a deep source. Either there are two, decoupled magmatic systems in the east rift zone, or there is a single system that extends to only a few kilometers depth. Third, a recent seismic tomography experiment sought to resolve the deep magmatic system in the east rift zone. It was unable to do so. Fourth, two episodes of aseismic fault slip have occurred in the last three years (the first in November 2000, the second in July 2003). These ``silent earthquakes,'' which are unmistakable in the continuous GPS record, are occurring on a structure that is no more than 4 or 5 km deep. If this structure is the so-called decollement, then the decollement is much shallower than previously thought. A much shallower decollement requires significantly lower slip rates to explain observed secular deformation. Lower slip rates eliminate the need for a deep east rift zone as a ``decoupler.'' Fifth, the standard model of south flank deformation fails to explain - indeed, even to address - the two most strikingly active structures on Kilauea: the Hilina and the Koa`e fault systems. We offer an alternative model of south flank deformation consisting of persistent creep on a hypothesized listric extension of the Hilina normal fault system. Not only is this model much simpler than the standard model, but it seems to make more sense mechanically. In the long term, we argue, the Hilina fault system behaves as a gravity-driven mass transport system, which moves both aseismically and in large earthquakes. We do not suggest that our alternative model for south flank deformation is a panacea or that it completely explains magmatic-tectonic interactions on Kilauea. Rather, we argue that our model is a more realistic starting point for future discussion about the origin of south flank deformation.
DE: 1208 Crustal movements--intraplate (8110)
DE: 7209 Earthquake dynamics and mechanics
DE: 8010 Fractures and faults
DE: 8020 Mechanics
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting