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Constraining fault-zone hydrogeology through integrated hydrological and geoelectrical analysis |
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| Authors: | Lyndsay B Ball Shemin Ge Jonathan Saul Caine André Revil Abderrahim Jardani |
| Institution: | 1. Department of Geological Sciences, University of Colorado at Boulder, 2200 Colorado Ave, CB 399, Boulder, CO, 80309, USA 2. US Geological Survey, Box 25046, MS 964, Denver, CO, 80225, USA 3. Department of Geophysics, Colorado School of Mines, 1500 Illinois Street, Golden, CO, 80401, USA 4. INSU-CNRS LGIT UMR 5559, Université de Savoie, Equipe Volcan, Domaine Universitaire, 73376, Le Bourget-du-Lac Cedex, France 5. M2C, UMR 6143, CNRS, Laboratoire Morphodynamique Continentale et C?tière, Université de Rouen, 76821, Mont Saint Aignan Cedex, France |
| Abstract: | The hydrogeologic influence of the Elkhorn fault in South Park, Colorado, USA, is examined through hydrologic data supplemented by electrical resistivity tomography and self-potential measurements. Water-level data indicate that groundwater flow is impeded by the fault on the spatial scale of tens of meters, but the lack of outcrop prevents interpretation of why the fault creates this hydrologic heterogeneity. By supplementing hydrologic and geologic data with geoelectrical measurements, further hydrogeologic interpretation is possible. Resistivity profiles and self-potential data are consistent with the interpretation of increased fracturing within 70 m of the fault. Further interpretation of the fault zone includes the possibility of a vertical groundwater flow component in a fractured and relatively high permeability damage zone and one or more relatively low permeability fault cores resulting in a conduit-barrier behavior of the fault zone at the meter to tens-of-meters scale. Calculated hydraulic heads from the self-potential data reveal additional complexity in permeability structure, including a steeper hydraulic gradient immediately west of the interpreted fault trace than suggested by the well data alone. |
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