HR: 1340h
AN: T13A-1352    [Abstracts]
TI: Rock Deformability, Brittle Fracture, and Strength Criteria in and Adjacent to the San Andreas Fault Zone; Applications to Tectonic Stress Estimation
AU: * Haimson, B c
EM: bhaimson@wisc.edu
AF: university of wisconsin, 1509 university avenue, Madison, WI 53706 United States
AB: A research project is underway at the University of Wisconsin-Madison, the principal objective of which is to investigate deformability, brittle fracture, and rock strength criteria adjacent to and inside the San Andreas Fault Zone. This laboratory study is being carried out on core extracted during the drilling of SAFOD. The rock mechanical properties characterized through this study are fundamental in efforts to understand the mechanisms that bring about earthquakes along the Fault. A unique true-triaxial apparatus is used to obtain realistic empirical strength criteria for the rocks represented by the extracted core. The true triaxial strength criterion is crucial to assessing the tectonic stress conditions when used in conjunction with the dimensions of borehole breakouts logged along the hole. These tests also provide necessary information on deformational properties such as elastic moduli, volumetric strain, dilatancy onset, as well as brittle fracture mechanism, of the exhumed fault and country rocks. The study seeks to answer questions such as how these rock properties vary across the fault zone and beyond; how they depend on environmental factors like in situ stress, mineralogy, pore pressure, and temperature; and how mechanical properties measured on core samples compare with properties inferred from borehole logs and surface-based geophysical observations. This comprehensive study will provide critical input of fundamental importance to SAFOD's scientific objectives of understanding fault zone processes and earthquake physics.
DE: 8164 Stresses--crust and lithosphere
DE: 5104 Fracture and flow
DE: 5112 Microstructure
DE: 5194 Instruments and techniques
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting