The Australia Legacy Geomagnetic Depth Sounding (GDS) collection brings together historical Australian GDS surveys and the closely related electromagnetic experiments that produced vertical magnetic-field transfer functions, acquired from 1966 to the early 2000s.
AWAGS 1989-90 Adelaide Geosyncline 1983-92 Ballarat 1992 Broken Hill 2002 CICADA97 induction array 1997-98 Carpentaria Array 1995 (Northern Sub-array) Carpentaria Array 1995 (Southern Sub-array) Central Australia 1976-77 Eyre Peninsula Northern Extension 1988 Halls Creek Orogen array 2000 Hanekup Eastern Queensland 2003 North East Tasmania induction study 1978-79 Robe-Mildura Coast Effect Profile 1976 SAMAS 1995 SWAGGIE land array 1998 SWAGGIE seafloor GDS 1998 Skippy-3 Array 1994 Southeast Australia array 1971 Southern Adelaide Geosyncline Pilot 1981-82 Southern Eyre Dense Array 1980-84 Southwest Australia Traverse 1966 Southwest Western Australia Array Tamar Anomaly Array 1983-84 Tasman Project land line 1983-84 Tasman Project seafloor line 1983-84 Western South Australia Array
The Australia Legacy Geomagnetic Depth Sounding collection brings together historical Australian geomagnetic depth sounding surveys, and the closely related electromagnetic experiments that produced vertical magnetic-field transfer functions, acquired from 1966 to the early 2000s. It currently holds 26 surveys and 592 stations, and preserves observations that document nearly four decades of Australian research into the electrical structure of the crust and lithosphere.
Geomagnetic depth sounding uses arrays of magnetometers recording the natural variations of the Earth's magnetic field to find where electric currents concentrate in the ground. Those measurements give transfer functions, drawn as induction arrows that point towards conductive rock, and these mapped the major Australian conductivity anomalies. Geomagnetic depth sounding came before magnetotellurics in Australia and was then run alongside it. The earliest member is the 1966 Perth to Rawlinna traverse of J. E. Everett and R. D. Hyndman across south-western Australia, which also carried the first magnetotelluric soundings reported in Australia. The 1971 Southeast Australia array followed, an early simultaneous regional array that detected the Victorian anomaly. Frederick (Ted) Lilley confirmed that anomaly in 1976 and named it the Otway anomaly. Through the 1970s and 1980s Flinders University ran coast-effect profiles and dense arrays across the southern Adelaide Geosyncline and Eyre Peninsula, and these mapped the Flinders and Eyre Peninsula anomalies. Australian National University arrays across central Australia found the Southwest Queensland anomaly. In Tasmania, the University of Tasmania's roving study of 1978 to 1979 and its array of 1983 to 1984 traced the Tamar anomaly.
By the 1980s and 1990s the experiments crossed regional and disciplinary boundaries. The Tasman Project recorded simultaneously from inland Australia across the Tasman Sea to the Lord Howe Rise between December 1983 and April 1984. Ian Ferguson's thesis records nine seafloor and nine land sites; eight of the land sites are served here. The Australia-Wide Array of Geomagnetic Stations of 1989 to 1990 took array depth sounding to the continental scale, with 54 portable magnetometers and the four AGSO observatories recording for more than a year. The 1995 Carpentaria arrays confirmed the northward continuation of the Southwest Queensland anomaly, and the structure they found was named the Carpentaria anomaly. SWAGGIE in 1998 combined 23 land magnetometers with seafloor instruments to follow the Eyre Peninsula anomaly across the continental shelf. Later arrays examined regional crustal structure in the Halls Creek Orogen and along the 2002 Broken Hill and Olary Domains profile. SAMAS and CICADA97 examined the effect of spatially varying geomagnetic fields on high-resolution aeromagnetic surveying.
At Flinders University, and later at the University of Adelaide, the arrays were the work of Francois Chamalaun, Antony White, Peter Milligan and Graham Heinson, with Sudhir Paul and S. K. Kusi behind the Adelaide Geosyncline and Eyre Peninsula arrays and Bob Walker behind the Flinders fluxgate magnetometer. The Australian National University arrays were the work of Lilley, Ferguson and Liejun Wang, and the Tasmanian studies the work of Wilfred Parkinson, Nazhar Buyung and Rahmat Hermanto at the University of Tasmania. AWAGS was run by Chamalaun with Charlie Barton at the Bureau of Mineral Resources.
Many of these observations survive only through legacy digital archives, published transfer functions, theses and institutional holdings. AusMT brings them together in one collection, with each survey an independent record carrying its own attribution, provenance and licence, so that they can be found and used alongside modern Australian electromagnetic datasets. The collection is therefore both a scientific dataset and a record of the development of electromagnetic geophysics in Australia.
Preservation and reprocessing
The largest single source is Liejun Wang's Australian Electromagnetic Database, compiled at the Australian National University, an induction-arrow register of 409 stations in 15 historical arrays. The other members come from the printed tables and appendices of the original publications and theses, and from surviving custodian holdings including the University of Adelaide legacy MT collection at NCI. Where the source printed transfer functions, the values come from its tables with the uncertainties it gives; where it printed none, they come from the register's induction-arrow rows. AWAGS alone is served from a modern reprocessing of its original one-minute recordings, which are held at Geoscience Australia.
Each survey record states where its transfer functions came from, and provenance is recorded at survey and station level, so a reprocessed, an original and a reconstructed transfer function can be told apart. Two arrays have no established acquisition date and no named investigator, and are listed after the dated surveys.
Data available
Data are provided through the individual surveys within this collection, with each survey retaining its own attribution, provenance and licence. Depending on the surviving source material, survey data may include newly reprocessed transfer functions, preserved original transfer functions, or transfer functions reconstructed from historical induction-arrow measurements.
The availability shown below summarises data across the collection; downloads are provided from the individual survey records.
Transfer functions
EDI archive (zip) · Survey MTH5 bundle
Member surveys
Each survey remains an independent AusMT record with its own metadata, provenance, attribution, licence and available data products.
Flinders University · 28 stations · GDS · 389 - 27,307 s
Where appropriate, surveys may be identified as:
Reprocessed: transfer functions newly estimated from surviving original time-series data.
Original: surviving historical transfer-function products preserved in their original or standardised form.
Reconstructed: modern transfer-function products reconstructed from archived induction-arrow measurements or other historical records.
Mixed: the survey contains data products from more than one of these sources.
Participating organisations
The organisations represented across this collection include institutions responsible for original acquisition, research, data preservation and subsequent custodianship. The organisation associated with an individual AusMT survey record identifies the custodian of that survey package and should not necessarily be interpreted as the sole organisation responsible for the original field acquisition.
