The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is a collaborative, national survey that acquires long-period magnetotelluric (MT) data. It is being conducted over multiple years, at approximately 3000 sites, to create the first national MT dataset in the world. This dataset will be an essential input to the Exploring for the Future programme as well as a valuable Earth imaging resource for researchers to reconstruct the tectonic evolution of the Australian continent.
AusLAMP assists with
- understanding the geological make up of Australia
- understanding how geological processes work
- geological hazard mapping such as earthquake risk
- analysing risks to Australia's electricity infrastructure
- helping to identify potential mineral and energy resources at a broad regional scale, not at a local property scale
This visionary project can only be achieved with the involvement of many government and research organisations. AusLAMP is led by Geoscience Australia in conjunction with the State and Northern Territory geological surveys, universities, and other research organisations. The long-period MT instruments are co-funded by AuScope and accessed through the ANSIR national earth-sounding instrument pool. Both AuScope and ANSIR organisations are funded by the Australian Government under the National Collaborative Research Infrastructure Strategy (NCRIS). The field data are acquired by these portable instruments on a half degree grid spacing (approximately 55km) during a deployment of about one-month to achieve maximum data and image to the base of the lithosphere (the rigid upper plate of the Earth). The acquisition phase of AusLAMP is expected to take several years to complete.
AusLAMP was launched in November 2013. To date, data have been acquired at nearly 1000 stations, which is approximately 30% of the national coverage. In Victoria, data acquisition was completed by the Geological Survey of Victoria and Geoscience Australia in 2014 and 2017. Data were acquired in Tasmania by the University of Tasmania, the Tasmanian Government, and Geoscience Australia in 2016. Data acquisition in South Australia was completed by a collaboration of the Geological Survey of South Australia, the University of Adelaide, and Geoscience Australia between 2014 and 2017.
Further data acquisition is ongoing. The Geological Survey of New South Wales and Geoscience Australia are currently collecting data in New South Wales. Geoscience Australia is also acquiring data in Northern Territory and Queensland as part of Geoscience Australia's $100.5 million Exploring for the Future programme.
Figure 1: The progress of AusLAMP data acquisition. Black lines - state\territory borders for Western Australia (WA), Northern Territory (NT), Queensland (QLD), South Australia (SA), New South Wales (NSW), Victoria (VIC) and Tasmania (TAS).
The MT data are collected using a passive geophysical technique that measures the Earth's electric and magnetic fields to determine the conductivity structure of the subsurface. Specialised equipment records MT signals for targeting depth of ten kilometres to hundreds of kilometres. The equipment does not output any signal to do this. For more detail on the MT method, MT site selection and setup, and data acquisition, see AusLAMP in detail.
Geoscience Australia archives all national AusLAMP MT data. Data and products will be released throughout the project life span. The released data will include processed data, inversion products, and reports. The data and associated products are freely available to the public, scientific research organisations, and industry.
Land Access for AusLAMP
AusLAMP requires Geoscience Australia staff, its collaborators and/or its contractors to access sites on various land holdings including farms, national parks and Indigenous lands. No land will be entered without prior consultation with land owners, and other relevant stakeholders.
AusLAMP includes almost 3000 sites across Australia. The proposed locations are selected to align with AusLAMP's Australia-wide project grid. Equipment is placed to suit terrain, with due consideration to your property operations. No access to your property is undertaken without prior consultation.
Following consultation with the land owners/managers all testing locations are accessed by either vehicle or helicopter. Existing roads and tracks are used as a priority, although some areas require off-road access.
No. The equipment is placed in a location in consultation with you (within a specified radius), to avoid disturbance. We aim to avoid locations with livestock, but where this is not possible the equipment is buried.
No. There will be minimal ground disturbance. Deployment sites are in open areas approximately 100 x 100m in size, away from human-made noise sources such as houses, electric fences, power lines and major roads. A 50cm deep hole is created with an auger for the sensor and if required, a 30cm x 50cm trench is dug to place the cables. The system runs from a fully-sealed 12 volt battery that is housed in a plastic box. As the equipment records naturally-occurring magnetic and electric signals there is no impact to flora or fauna. All project staff considers weed management when entering properties and will undertake specific measures to prevent the spread of weeds.
No. Geoscience Australia and their representatives are fully responsible for the equipment. While all due care should be taken, the land owner/manager is not responsible for any damage/theft of the equipment.
The field crew are trained and experienced operators. They are fully insured and will take full responsibility during the survey for occupational health and safety.
AusLAMP is not providing the high-resolution, near-surface data required by mineral or energy companies for exploration purposes. AusLAMP is a non-commercial research project that will image broad geological features at depths greater than 10 kilometres. As with any geoscience information, AusLAMP results could be used by companies to better understand geological regions of interest.
All data and results will be released to the public and will be available free of charge.
For more information contact Geoscience Australia staff via email, firstname.lastname@example.org.
AusLAMP in detail
AusLAMP is a long-period magnetotelluric survey (MT) aimed to image the electrical conductivity/ resistivity structure of Australian continent lithosphere in three dimensions (3D), and to identify and characterise major geological structures in the crust and upper mantle. The survey results will provide new insight and valuable information for the Australian continent lithosphere framework and address fundamental questions, such as how the current geological structure was established, the nature of the geological processes, and how large-scale crustal and lithospheric structures control mineral deposition and hydrocarbon basin formation. The MT survey results can be integrated with other national datasets, such as aeromagnetic, gravity, seismic tomography, geochemical, and geological datasets. The integration of these multidisciplinary datasets will help to develop a better scientific understanding of the lithospheric architecture and evolution of the Australian continent, highlighting prospective areas for mineral and energy resources at a regional scale, as well as to assess geoelectric and other geological hazards.
Magnetotelluric (MT) method
The magnetotelluric (MT) method is a passive geophysical technique that measures variations of the Earth's naturally occurring magnetic and electric field to determine the electrical resistivity distribution of the subsurface, from depths of tens of meters to hundreds of kilometres. The MT source fields are generated by world-wide thunderstorm activity (mainly lightning discharges at a frequency above 1 Hz) and the interactions between the solar wind and the Earth's magnetic field in the magnetosphere and ionosphere (at a frequency less than 1 Hz). These sources provide a rich spectrum of source fields in the band 10-5 to 104 Hz, which are suited for crust and upper mantle study. These signals vary in strength over hours, days, weeks and over the sunspot cycle.
The time-series measurements of the magnetic and electric field are converted to a set of frequency responses through Fourier transformation, the lower the frequency the deeper the source of the Earth response. In order to image the deep crust and upper mantle it is necessary to measure very low frequencies to achieve sensitivity to the base of the lithosphere. Using this data a 3D Earth electrical conductivity model can be generated by sophisticated mathematical inversion algorithms on high performance computers.
The MT method is widely used for mineral, petroleum, geothermal exploration, and crust and mantle study. The main strengths of the method are that it allows a broader range of investigation depths than other geophysical techniques, and it has a greater level of sensitivity to lateral and vertical electrical conductivity variations. It is useful for distinguishing different types of rock and helping to understand geological structures and tectonic evolution.
AusLAMP data acquistion
The AusLAMP survey collects long-period MT data by portable instruments on a grid of approximately 55km (half degree geodetic). The portable instrument uses a three-component fluxgate magnetometer and dipoles with electrodes to record continuous magnetic and electric signals in the field. The targeting signal range is 10 s - 10000 s, which is an investigation depth from a few kilometres to hundreds of kilometres. To ensure the MT measurement captures good natural signals at longer periods, data is collected for one month at each site. Multiple stations are recorded simultaneously for the purposes of remote reference and improving quality of processing data.
A typical MT station is shown below. Deployment sites are in open areas approximately 100 x 100m in size, away from human-made noise sources such as houses, electric fences, power lines and major roads.
The instrumentation deployed is made up of:
- A data acquisition box containing a data recording unit, GPS and 12 volt battery.
- Five small electrical sensors (electrodes) buried 20cm in depth spaced 50m apart on a north, south, east and west axis. These sensors are connected to the acquisition box with a cable, and where required, the cable is buried.
- A magnetic sensor (magnetometer) buried 40cm in depth and connected to the acquisition box by a 20m cable, which is also buried.
- A small solar panel is mounted close to the acquisition box to charge the battery.
For further information contact Geoscience Australia staff via email, email@example.com