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Title: Joint interpretation of seismic and electromagnetic results, investigating zero age oceanic crust
Author: Greer, A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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We developed a joint interpretation method to allow us to combine the geophysical constraints from seismic and controlled source electromagnetic (CSEM) experiments. We used effective medium techniques to represent the bulk elastic and electric properties of a two-phase composite material, by describing the microstructure and the relative volumes of each phase. We used the misfit, from a calculated value of rock property to a geophysically observed value. The misfit is calculated from both elastic and electric properties of the rock, providing a common variable with which to combine the seismic and controlled source electromagnetic (CSEM) constraints. We applied the joint interpretation technique to geophysical results from the East Pacific Rise, Reykjanes Ridge and the Valu Fa Ridge, providing estimates for fluid fraction, degree of interconnectivity of the fluid phase and pore geometry. Prior to developing the joint interpretation method we revisited the East Pacific Rise CSEM dataset, using more developed modelling methods with fresh information regarding the phase drift of the electromagnetic source. We concluded that the presence of a magma chamber was not required by the dataset, as did the original interpretation. However, we accept a small magma chamber (tens of metres) would not be resolved by the CSEM technique. Our results contrast with original seismic results suggesting the presence of a large magma chamber (>1km wide). However, later reworking of the seismic dataset has suggested the presence of a much smaller magma chamber. We believe that with careful assessment of the limitations of each technique the results are mutually satisfactory.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available