AusMT / surveys / KUTh Tamar Valley 2008

KUTh Tamar Valley 2008 BBMT

Magnetotelluric survey · Tasmania · Mineral Resources Tasmania

A broadband magnetotelluric transect of 42.

About this survey

A broadband magnetotelluric transect of 42.0 km on a bearing of 065 degrees was acquired across the Tamar Valley north of Launceston, Tasmania, between 13 September and 16 October 2008, crossing the Tamar River and the Tamar Conductivity Zone. Moombarriga Geoscience Pty Ltd acquired it for KUTh Exploration Pty Ltd, a subsidiary of KUTh Energy Ltd, as geothermal exploration on special exploration licence SEL26/2005, since surrendered. Sites were laid out along the line at a median spacing of 1.08 km, and two further sites about 2 km off the line were added to trace an unknown noise source affecting the electric field between sites 32 and 37. Three days into the line, cultural noise led the contractor to install a remote reference station at Oatlands, about 116 km south beside the proposed drill hole, on 1 October 2008; it recorded continuously to the end of the survey and most of the line was processed against it.

Recording used Phoenix Geophysics MTU-5A receivers with MTC-50 induction coils, four receiver boxes numbered U-2189 to U-2192, logging Ex, Ey, Bx and By at every site and Bz at 33 of the 40, at three sample rates of 15, 150 and 2400 Hz, with 50 Hz notch filters and electric dipoles of 54 to 95 m. The acquisition report specifies a minimum of 16 hours of recording at each site, aimed at resolving apparent resistivity and phase to a period of 100 seconds; the headers of the files served here give occupations of 15.1 to 54.0 hours, with a median of 20.4 hours. All induction coils were calibrated before the survey and those calibrations were used in processing. Transfer functions were estimated with the Phoenix SSMT suite, using the coherence based rejection of Jones and Jodicke (1984) and, at most sites, the remote reference method of Gamble, Goubau and Clarke (1979), then cross power edited in MT-Editor version 0.99.2.68.

This package serves the 40 transfer functions lodged for the northern line: 39 line sites and the Oatlands remote reference, each a Phoenix cross-spectra file. Thirty eight carry 80 frequencies from 320 Hz to 0.00034 Hz, NTL029A carries 78 from 320 Hz to 0.0005 Hz, and the Oatlands file carries 88 from 320 Hz to 0.000086 Hz. Four of the 40 are served here but withheld from the published products: at NTL025A, NTL031A, NTL032A and NTL036A the magnetic sensors were laid rotated against the electric dipoles while the spectra declare a zero rotation, so the frame the spectra are stored in cannot be determined from the file.

Data origin. The files served here are the 40 members of Northern2008/EDIs/NTL_EDI/ inside Northern2008.zip, in Appendix7_MT_Data of Mineral Resources Tasmania company report 09_5904, whose acquisition volume is MRT record 09_5904A, webdoc id 88062, "Magnetotelluric Survey Report for KUTh Exploration PL" by Evans, S., dated 27 October 2008. They are released under Creative Commons Attribution 3.0 Australia, the licence Mineral Resources Tasmania applies to its data releases. The raw Phoenix time series behind them, the recording tables and the box and coil calibrations remain inside that same archive at Mineral Resources Tasmania and are not served here.

Data and downloads

Stations (36)

Contributors and organisations

Organisation

Mineral Resources Tasmania

Licence

CC BY 3.0 AU

Instruments

Phoenix Geophysics MTU-5A
Phoenix Geophysics MTC-50

Processing

Phoenix SSMT

Funding

KUTh Exploration Pty Ltd

Publications

Ostersen T C H (2021). Geoelectric Structure of the Tasmanian Lithosphere from Multi-Scale Magnetotelluric Data. PhD thesis, University of Tasmania. 10.25959/100.00037925

Identifiers and provenance

Machine-readable survey record · catalogue schema mtcat 2.0