Tidal influence on self-potential measurements

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Title: Tidal influence on self-potential measurements
Authors: MacAllister, DJ
Jackson, MD
Butler, AP
Vinogradov, J
Item Type: Journal Article
Abstract: Long-term surface and borehole self-potential (SP) monitoring was conducted in the UK Chalk aquifer at two sites. The coastal site is ~1.7 km from the coast, and the inland site is ~80 km from the coast. At both sites, power spectral density analysis revealed that SP data contain the main ocean tidal periodic components. However, the principal lunar component (M2), the dominant ocean tidal component, was most significant at the coastal site. The M2 signal in surface-referenced SP data at the inland site was partly due to telluric currents caused by the geomagnetic ocean dynamo. Earth and/or atmospheric tides also contributed, as the SP power spectrum was not typical of a telluric electric field. The M2 component in borehole-referenced data at the inland site was below the significance level of the analysis method and was 2 orders of magnitude smaller than the M2 signal in borehole-referenced SP data at the coastal site. The tidal response of the SP data in the coastal borehole is, therefore, primarily driven by ocean tides. These cause changes in fluid pressure and chemical concentration gradients within the coastal aquifer, leading to time varying electrokinetic and exclusion-diffusion potentials. Borehole-referenced SP measurements could be used to characterize and monitor tidal processes in coastal aquifers such as the intrusion of seawater.
Issue Date: 3-Dec-2016
Date of Acceptance: 7-Nov-2016
URI: http://hdl.handle.net/10044/1/42374
DOI: https://dx.doi.org/10.1002/2016JB013376
ISSN: 2169-9313
Publisher: American Geophysical Union
Start Page: 8432
End Page: 8452
Journal / Book Title: Journal of Geophysical Research. Solid Earth
Volume: 121
Issue: 12
Copyright Statement: ©2016. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: Total E&P UK Limited
Funder's Grant Number: Contract Number: 4300002692
Publication Status: Published
Open Access location: https://authorservices.wiley.com/api/pdf/fullArticle/13696353
Appears in Collections:Faculty of Engineering
Civil and Environmental Engineering
Earth Science and Engineering

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