HR: 1340h
AN: H23A-1019    [Abstracts]
TI: Characterizing Fault Zone Permeability Through Integrated Geophysical and Hydrological Data, Elkhorn Fault, Park County, Colorado
AU: * Ball, L B
EM: lyndsay.ball@colorado.edu
AF: University of Colorado at Boulder, 2200 Colorado Ave. Campus Box 399, Boulder, CO 80309, United States
AU: * Ball, L B
EM: lyndsay.ball@colorado.edu
AF: U.S. Geological Survey, Denver Federal Center Box 25046, MS 964, Denver, CO 80225, United States
AU: Ge, S
EM: ges@colorado.edu
AF: University of Colorado at Boulder, 2200 Colorado Ave. Campus Box 399, Boulder, CO 80309, United States
AU: Caine, J S
EM: jscaine@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center Box 25046, MS 964, Denver, CO 80225, United States
AB: Fault zones are ubiquitous in ground-water aquifers and can play a significant role in fluid transport at local to regional scales. Fault-zone permeability structure controls whether the fault behaves as a barrier, conduit, or combined barrier-conduit for fluid flow. Much work has been done to measure local- to well-scale permeability of faults. However, hydrogeologic heterogeneity prevents local-scale measurements from accurately characterizing the regional hydrogeologic impact of fault zones. Near-surface geophysical techniques provide an estimate the distribution and continuity of subsurface fault zone properties, allowing for the identification of structural heterogeneities that may cause heterogeneities in permeability. This research focuses on the integration of geophysical and hydrological techniques to characterize the regional hydrogeologic effects of the Elkhorn Fault in Park County, Colorado. The Elkhorn fault is a Laramide-aged thrust fault with a sedimentary foot wall and fractured Proterozoic, crystalline hanging wall. Magnetic, gravity, and resistivity data are used to constrain the location and geometry of the fault as well as to aid in the interpretation of the structural and hydrogeologic complexity of the fault and its associated damage zone. The combined geophysical interpretation provides a framework for the development of a physical domain in which pumping test and time-series hydrologic data can be used to evaluate permeability. This interpretation also serves as a guideline for the placement of wells, facilitating direct hydrological testing of the in-situ permeability of different components of the fault zone. By utilizing geophysical techniques, hydrological data may be more effectively collected and interpreted, leading to the development of ground-water-flow models that more accurately depict the regional hydrogeologic effect of the Elkhorn fault.
DE: 0925 Magnetic and electrical methods (5109)
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
DE: 5114 Permeability and porosity
DE: 8010 Fractures and faults
SC: Hydrology [H]
MN: 2007 Fall Meeting