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Understanding the geodetic signature of large aquifer systems: Example of the Ozark Plateaus in Central United States
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  • Stacy Larochelle,
  • Kristel Chanard,
  • Luce Fleitout,
  • Jerome Nicolas Fortin,
  • Adriano Gualandi,
  • Laurent Longuevergne,
  • Paul Rebischung,
  • Sophie Violette,
  • Jean-Philippe Avouac
Stacy Larochelle
California Institute of Technology, California Institute of Technology

Corresponding Author:stacy.larochelle@caltech.edu

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Kristel Chanard
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Luce Fleitout
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Jerome Nicolas Fortin
Ecole Normale Supérieure, Ecole Normale Supérieure
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Adriano Gualandi
Istituto Nazionale di Geofisica e Vulcanologia, Istituto Nazionale di Geofisica e Vulcanologia
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Laurent Longuevergne
CNRS - Université Rennes 1, CNRS - Université Rennes 1
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Paul Rebischung
Institut National de l'Information Géographique et Forestière (IGN), Institut National de l'Information Géographique et Forestière (IGN)
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Sophie Violette
Université Pierre et Marie CURIE-Sorbonne Universités & CNRS, Université Pierre et Marie CURIE-Sorbonne Universités & CNRS
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Jean-Philippe Avouac
California Institute of Technology, California Institute of Technology
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The continuous redistribution of water mass involved in the hydrologic cycle leads to deformation of the solid Earth. On a global scale, this deformation is well explained by redistribution in surface loading and can be quantified to first order with space-based gravimetric and geodetic measurements. At the regional scale, however, aquifer systems also undergo poroelastic deformation in response to groundwater fluctuations. Disentangling these related but distinct 3D deformation fields from geodetic time series is essential to accurately invert for changes in continental water mass, to understand the mechanical response of aquifers to internal pressure changes as well as to correct time series for these known effects. Here, we demonstrate a methodology to accomplish this task by considering the example of the well-instrumented Ozark Plateaus Aquifer System (OPAS) in central United States. We begin by characterizing the most important sources of signal in the spatially heterogeneous groundwater level dataset using an Independent Component Analysis. Then, to estimate the associated poroelastic displacements, we project geodetic time series corrected for surface loading effects onto orthogonalized versions of the groundwater temporal functions. We interpret the extracted displacements in light of analytical solutions and a 2D model relating groundwater level variations to surface displacements. In particular, the relatively low estimates of elastic moduli inferred from the poroelastic displacements and groundwater fluctuations may be indicative of surficial layers with a high fracture density. Our findings suggest that OPAS undergoes significant poroelastic deformation, including highly heterogeneous horizontal poroelastic displacements.
Mar 2022Published in Journal of Geophysical Research: Solid Earth volume 127 issue 3. 10.1029/2021JB023097