Electrical Conductivity Structure in the South-east Australian Region

An array of variometers across south-east Australia has recorded natural magnetic variations having power in a frequency band of 0·04—10 cycles/hr. The set data have outlined two major regions of high terrestrial electrical conductivity (σ); the first beneath the sea floor off the Australian south-east coast; the second in the vicinity of the most recent eruptive centres of the ‘Newer Volcanics’ in western Victoria. Both regions may indicate low Q upper mantle zones. Daily variation data provide significant control on permissible conductivity models.