Electromagnetic induction studies in the Eyre Peninsula

• Main Authors: South Australia, Robert Kusi, Antony White, Graham Heinson, Peter Milligan
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: shown by small black dots in Fig. 2. White & Milligan (1984; Antarc*; Antarctica
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1033.5761; http://gji.oxfordjournals.org/content/132/3/687.full.pdf

Chamalaun (1989), were included in the analysis. A major conductive feature in the crust, first noted by White & Milligan (1984) as the Eyre Peninsula Anomaly (EPA), is re-examined to assess its continuity to the north of the original arrays and to investigate its relationship with major tectonic features. Magnetic-field time-series were converted to induction arrows in the frequency domain. These induction arrows were initially inverted using the minimum-structure 2-D Occam approach to estimate the electrical conductance of the crust. Following this, thin-sheet forward modelling was used to examine the relationship between the conductance and the dominant tectonic features. The principal results of the modelling are that a narrow conductive feature extends inland from the coast about 160 km before terminating, and the conductance is in the range 3000 to 10 000 S, which decreases inland. A strong correlation exists between the electrical conductance of the Eyre Peninsula and Bouguer gravity anomalies, and in particular the EPA is coincident with a significant Bouguer gravity gradient. There is also good agreement between the locations of the foci of earthquakes of magnitude greater than 4.0 and the EPA. We believe that the anomaly is associated with a geological fracture in the Precambrian upper crust as a result of crustal extension prior to the rifting of Australia from Antarctica in the Jurassic (160 Ma).