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Improved imaging of ground deformation and brine seepage around abandoned flooded salt mines by joint inversion of multiphysics data

Max A. Meju, Bernd Kulessa Orcid Logo, Luis Gallardo, Sarah Thompson, Alastair Ruffell, Kieran Parker

Journal of Applied Geophysics, Volume: 219, Start page: 105217

Swansea University Author: Bernd Kulessa Orcid Logo

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Abstract

Centuries of bad mine-flooding practice have left a legacy of underground salt mine collapse and contaminated discharges, the scale of which is only slowly being revealed now that ground processes have caused instability over decades to >100 years. Geophysical methods are used for mapping ground...

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Published in: Journal of Applied Geophysics
ISSN: 0926-9851
Published: Elsevier BV 2023
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa64787
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Abstract: Centuries of bad mine-flooding practice have left a legacy of underground salt mine collapse and contaminated discharges, the scale of which is only slowly being revealed now that ground processes have caused instability over decades to >100 years. Geophysical methods are used for mapping ground subsidence and groundwater contamination at such sites but suffer individually from non-uniqueness and with the underlying mechanism and processes not being well understood. Here, to reduce uncertainty and maximize accuracy we recover subsurface models with structural similarity enforced via crossgradients joint inversion of seismic refraction and dc resistivity data for the top 40 m at former mining areas in Carrickfergus region of Northern Ireland. The models in combination with multispectral image fusion, enable us to identify hitherto unknown mechanism of deformation and compositional changes consistent with the Chebotarev geochemical evolution of groundwater. We found evidence of concealed gravitational slump structures interpreted as being caused by water ingress weakening the gypsum-bearing marl bedrock (via gypsum dissolution and increased fluid pressures within marl) and leading to gravitational gliding deformation, expressed as curved subsidence bands and stepped thrusts coincident with surface zones of brine-mud seepage and sinkhole collapse. Our results have wide-ranging implications for best-practice assessment and management of abandoned flooded salt mines and the hazards they pose to ground stability and water resources world-wide.
Keywords: Hydrogeophysics, Joint inversion, Electrical resistivity, Seismic velocity, Ground instability, Groundwater contamination
College: Faculty of Science and Engineering
Funders: Swansea University
Start Page: 105217