A Magnetometer Array Study Across Southern Victoria and Bass Strait Area, Australia

Abstract

A second magnetometer array study in south‐east Australia has clarified anomalous effects discovered earlier, and revealed a linear conductor striking south‐west‐north‐east under or nearby the Otway Ranges. The anomalous effects are most strongly present in variation fields of period about one hour, but persist to the longer periods of the quiet daily variation. At the shortest periods studied, of order several minutes, the anomalous effects are weak. The conductor is approximately coincidental with a zone of continental seismicity, and may be due to rock fracture and dilation or to the presence of a diapir of magma beneath the seismic zone. The existence of an upper mantle hotspot in the area has been speculated. In interpreting the observed array data, use is made of a method for separating anomalous fields from regional fields, based on inspection of polar diagrams. The anomalous components of horizontal field are especially diagnostic, and for one station it is possible to construct special polarization ellipses for them. This paper covers the full frequency range possible with simple vario‐meters, from pulsation events, through substorms, to quiet days. Copyright © 1976, Wiley Blackwell. All rights reserved