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Electromagnetic investigation of the Lucky Strike Seamount near 37°N, Mid-Atlantic Ridge

Electromagnetic investigation of the Lucky Strike Seamount near 37°N, Mid-Atlantic Ridge
Electromagnetic investigation of the Lucky Strike Seamount near 37°N, Mid-Atlantic Ridge

In October 1999, a controlled source electromagnetic (CSEM) survey was carried out over the central seamount of the Lucky Strike segment of the Mid-Atlantic Ridge.  The summit of this seamount has been a target for biological, geochemical and surface geophysical research since hydrothermal activity was first discovered there in 1992.  However, this survey was the first attempt to use geophysical techniques to constrain sub-seafloor crustal properties.  This dissertation describes the progress that has been made in analysing the CSEM data.

1-dimensional forward modelling and inversion have proven useful tools in constraining the bulk resistivity of the region, and highlight subsets of the data that are particularly worthy of further study.  The data are to first order consistent with a ˜700 m-thick layer of 4.4-7.0 «problem!»m overlaying a crustal resistivity of at least 100 «problem!»m.

The effect of the Lucky Strike topography was investigated using 2-dimensional forward modelling.  Topography was found to have only a minor effect on most of the data. Portions of data that are severely influenced by topographic variations were identified and removed.  Subsequent modelling could then be carried out assuming a flat seafloor.

2-D inversion was found to be of little use in constraining lateral resistivity variations:  3-dimensional resistivity anomalies were mapped into the 2-D models, producing large tradeoffs in data residuals.  However, good progress was made with pseudoimaging of 1-D residuals, and 3-D forward modelling.  A 2 km-wide region with anomalously low resistivities has been identified over the region of known hydrothermal activity.  There is also evidence for another region of high resistivities over the north west of the seamount.  Co-incident with a small topographic high, this may be due to a hitherto unknown region of hydrothermal activity.  Resistivities increase rapidly to the east, over the eastern flank of the seamount.

University of Southampton
Barker, Neville
bc6cd626-9e0c-4563-b154-0fd2052b04d3
Barker, Neville
bc6cd626-9e0c-4563-b154-0fd2052b04d3

Barker, Neville (2004) Electromagnetic investigation of the Lucky Strike Seamount near 37°N, Mid-Atlantic Ridge. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

In October 1999, a controlled source electromagnetic (CSEM) survey was carried out over the central seamount of the Lucky Strike segment of the Mid-Atlantic Ridge.  The summit of this seamount has been a target for biological, geochemical and surface geophysical research since hydrothermal activity was first discovered there in 1992.  However, this survey was the first attempt to use geophysical techniques to constrain sub-seafloor crustal properties.  This dissertation describes the progress that has been made in analysing the CSEM data.

1-dimensional forward modelling and inversion have proven useful tools in constraining the bulk resistivity of the region, and highlight subsets of the data that are particularly worthy of further study.  The data are to first order consistent with a ˜700 m-thick layer of 4.4-7.0 «problem!»m overlaying a crustal resistivity of at least 100 «problem!»m.

The effect of the Lucky Strike topography was investigated using 2-dimensional forward modelling.  Topography was found to have only a minor effect on most of the data. Portions of data that are severely influenced by topographic variations were identified and removed.  Subsequent modelling could then be carried out assuming a flat seafloor.

2-D inversion was found to be of little use in constraining lateral resistivity variations:  3-dimensional resistivity anomalies were mapped into the 2-D models, producing large tradeoffs in data residuals.  However, good progress was made with pseudoimaging of 1-D residuals, and 3-D forward modelling.  A 2 km-wide region with anomalously low resistivities has been identified over the region of known hydrothermal activity.  There is also evidence for another region of high resistivities over the north west of the seamount.  Co-incident with a small topographic high, this may be due to a hitherto unknown region of hydrothermal activity.  Resistivities increase rapidly to the east, over the eastern flank of the seamount.

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Published date: 2004

Identifiers

Local EPrints ID: 465225
URI: http://eprints.soton.ac.uk/id/eprint/465225
PURE UUID: 415b004f-0abb-4299-963e-77d1951ced0d

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Date deposited: 05 Jul 2022 00:30
Last modified: 26 Oct 2023 01:46

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Author: Neville Barker

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