The total-field geomagnetic coast effect in southeast Australia
Speaker:Ying-Yuan Li
Abstract
Near most coastlines the vertical component of the geomagnetic variation field is abnormally large and correlates positively with the inland horizontal component.
This phenomenon is known as the geomagnetic coast effect. The few coastal locations at which it is absent are tectonically anomalous. The ratio of vertical to horizontal components decreases inland at a rate which depends on the geological nature of the continent.
In the CICADA97 experiment a line of simultaneously recording stationary vector magnetometers was deployed from inland NSW, across the east Australian coast, and into the Tasman Sea. The purpose of the experiment was to investigate the effect of electrical conductivity structure near a coastline on natural time variations in Earth¡¦s magnetic field. Aeromagnetic surveys regularly take place in such coastal areas, and removal of time variations of the magnetic field is a prime task of data reduction. CICADA97 data show that long-period variations of the total field are systematically enhanced near the NSW coast, while spatial patterns of short-period variations (such as pulsations) may be strongly influenced by electrical conductivity structures on a smaller scale, such as bays and inlets.
Lilley, F., White, A., and Heinson, G., 2000. The total-field geomagnetic coast effect: The CICADA97 line from deep Tasman Sea to inland New South Wales. Exploration Geophysics, 31, 52-57.
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