HR: 0800h
AN: V21D-0658    [Abstracts]
TI: Do Flexural Stresses Explain the Mantle Fault Zone Beneath Kilauea Volcano?
AU: * Pritchard, M E
EM: mp337@cornell.edu
AF: Department of Earth and Atmospheric Sciences, Snee Hall Cornell University, Ithaca, NY 14853 United States
AU: Rubin, A M
EM: arubin@princeton.edu
AF: Department of Geosciences, Guyot Hall Princeton University, Princeton, NJ 08544 United States
AU: Wolfe, C J
EM: wolfe@hawaii.edu
AF: Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, HI 96822 United States
AB: Recent relocation and focal mechanism analyses of deep earthquakes beneath Kilauea volcano, Hawaii indicates that seismicity is concentrated on a horizontal fault zone at a depth of 30 km, with seaward slip on a low-angle plane. We discuss whether the observed localization of the earthquakes can be explained solely by stresses induced by flexure of the Pacific plate beneath the Hawaiian load, or if other perturbations of the stress field are required. We find that flexural stresses are consistent with the observed fault plane orientation, and the direction and rate of slip. However, the model has four shortcomings: (1) the fault zone is displaced 15-20 km to the NW of the region of predicted maximum shear stress. (2) The maximum shear stress in the vicinity of the fault zone seems too low to overcome Coulomb friction (by about a factor of 2, assuming hydrostatic pore pressure). (3) The fault zone is much more localized laterally than is the region of large flexural stresses and stressing rates. (4) The fault zone is more localized vertically than might be inferred from the calculation as well. Simple and plausible extensions of the plate flexure model by accounting for spatial variations in the location of pore fluids, and/or the possible existence of a passive shear-stress free magma transport sytstem can overcome most of these shortcomings. Several magma pipes would be necessary to explain the observed earthquake locations, and simple thermal arguments indicate that such pipes could be conduits for porous flow if they are a few km in radius.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8138 Lithospheric flexure
DE: 8145 Physics of magma and magma bodies
DE: 8164 Stresses: crust and lithosphere
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005