Woods Hole Oceanographic Institution

Dr Rob. L. Evans

»Electrical Structure of the Central Cascadia Subduction Zone: The EMSLAB Lincoln Line Revisited
»Electrical Lithosphere Beneath the Kaapvaal Craton
»Gulf Of Mexico Gas Seep
»MELT MT Results
»Wrightsville Beach Geophysics and Hydrology
»MELT Area Off-Axis Structure
»Karst Formation off North Carolina
»Review of Shallow Offshore EM Work
»Towed EM System
»EPR MMR Experiment
»Offshore MT and Subduction Systems
»Shallow Porosity Structure on the Continental Shelf
»Oceanic and Continental Mantle Resistivity
»New Jersey EM Survey
»Eel River EM Survey
»Impact of groundwater on EM data
»Electrical structure of Slave Craton
»Report of Shoreline Change Workshop

Rob. L. Evans, Measuring the Shallow Porosity Structure of Sediments on the Continental Shelf: A comparison of an Electromagnetic Approach with Cores and Acoustic Backscatter, J. Geophys. Res. , vol 106, 2001

We validate estimates of shallow sedimentary porosities made on the continental shelf by electromagnetic methods through a comparison with those measured directly in cores. Specifically, we show that an electromagnetic surveying system we have used to measure sediment resistivity in a number of seafloor locations returns porosity depth profiles that are related to those measured in cores, and that our data have good sensitivity to the structure within the upper-most few tens of centimeters of seafloor. We then consider inferences of sediment type made by observations of acoustic backscatter in the light of our porosity measurements. Our results suggest that electromagnetic methods provide complimentary information that can be used to improve grain type estimates at and just below the seafloor, especially when combined with acoustic backscatter data. Because the system is pulled along the seafloor, data can be quickly collected from a large area of seafloor and can be used to interpolate facies conditions between core locations.

FILE » 2000JC000487_7968.pdf

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