The application of Time-Lapse Microgravity for the Investigation and Monitoring of Subsidence at Northwich, Cheshire

Branston, Michael W. and Styles, Peter (2003) The application of Time-Lapse Microgravity for the Investigation and Monitoring of Subsidence at Northwich, Cheshire. Quarterly Journal of Engineering Geology and Hydrogeology, 36 (3). pp. 231-244. DOI: https://doi.org/10.1144/1470-9236/03-243

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Official URL: http://doi.org/10.1144/1470-9236/03-243

Abstract

Peter Street is an area of terraced houses in Northwich suffering from subsidence, thought to be related to salt extraction in the 19th century. Microgravity and resistivity profiling have been used as non-invasive techniques to investigate the cause of this subsidence. Repeat (or time-lapse) microgravity has been used to assess the stability and evolution of the low-density areas. Time-lapse microgravity uses the characteristics of anomaly size and gradient to track the development of cavities as they propagate to the surface. It is possible to monitor the change in gravity with time and to model the increase in cavity volume and/or depth. A gravity low was found to be coincident with the area experiencing subsidence. Integrated modelling techniques including Euler deconvolution, Cordell and Henderson inversion and GRAVMAG modelling have been used to investigate the depth and size of the body responsible for this anomaly. Resistivity imaging has been used to investigate the conductivity of the near surface and constrain the gravity models. Results from both techniques suggest that low density ground is now present at a depth of 3-4 m below the surface in the subsidence affected area. The use of time-lapse microgravity has shown that there has been an upward migration of a low-density zone at gravity anomaly C over the monitoring period.

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Item Type: Article
Subjects: Methodology > Other-additional study
Region > UK > Cheshire
Inducing technology > Underground mining
Project: EPOS-IP > NORTHWICH: underground salt extraction cavities
EPOS-IP > PREESALL MINE: underground salt extraction cavities