Southeast Lachlan Deep Crustal Seismic Reflection Survey
The Geological Survey of Victoria (GSV) conducted a low impact regional deep seismic reflection survey in eastern Victoria, during March and April 2018.
The survey forms a major part of a government-funded collaborative scientific research program. It was carried out in collaboration with Geoscience Australia, Geological Survey of New South Wales and AuScope.
Location of the survey
For about two months a convoy of survey trucks moved slowly through the region along three routes:
- Starting south of Benalla and travelling approximately 306 kilometres eastwards towards Tom Groggin and into New South Wales.
- Starting north of Benambra and travelling approximately 154 kilometres southeastwards to near Bonang.
- Starting west of Bonang and travelling approximately 45km east through Bendoc, continuing east to the coast south of Eden in New South Wales.
These routes are marked in purple on the below map.
What is deep seismic reflection?
Deep seismic reflection is an acoustic technique similar to medical ultrasound scanning and does not cause any damage to the land.
Vibrating plates are attached to specialised trucks and the plates deliver sound down into the ground. Echoes from geology within the earth are then recorded by an array of specialised microphones (called geophones).
This data allows us to see the shapes and positions of hidden structures – in this instance the large-scale shapes of rock formations and fault structures to about 50kms depth in the earth's crust.
What will we do with the data?
The collected seismic data has been processed into images. Geological interpretation of the images will be undertaken by the research team prior to public release of all the data and interpretations later this year.
This survey is part of a long-term program to build large-scale knowledge of Victoria's geological architecture and will focus on rock types, faults and their distribution.
This is the third such seismic reflection survey conducted by the GSV. Two previous deep seismic reflection surveys were conducted in 2006 and 2009 in central and western Victoria respectively.
We are planning to carry out a ground gravity survey later this year along the same route. The gravity survey is far less intensive than the seismic survey and will be completed in significantly less time.
Gravity data complements seismic reflection data by giving geoscientists additional information on the density properties of rocks hidden within the crust. Multiple complementary datasets help produce better quality interpretations of geology.
Updates regarding the timing and progress of the gravity survey will be published here over the coming months.
Frequently asked questions
Under Victorian laws, surveyors engaged by the Geological Survey of Victoria (GSV) were given the right to carry out this research. This seismic survey was authorised under Section 112 (1) of the Mineral Resources (Sustainable Development) Act 1990.
The seismic survey work was overseen by the department. A range of other Victorian government authorities were been consulted, such as Parks Victoria, the Department of Environment, Land, Water and Planning, VicRoads and local councils.
No. Three Vibroseis trucks drove slowly in convoy along the survey route, stopping at frequent intervals to generate the seismic signal by synchronously vibrating the ground beneath them for 10 to 15 seconds. The vibrations were about the same as those generated by a large truck driving past.
Three trucks were required to generate sufficient seismic energy to see deep into the earth. The trucks were pre-programmed so that vibrations were only generated at the pre-determined points. The vibrations were generated clear of buildings and significant infrastructure.
The highly sensitive geophones were embedded in the surface to a depth of approximately 100-150 millimetres to minimise the detection of noise on the surface when listening for the echoes from great depth.
The survey sites were chosen by scientists where more data is needed to understand the region’s geology and how it has evolved over time.
The survey lines were designed across the region to be as straight as possible to achieve the best scientific result.
The data will be incorporated into the existing state and national seismic databases. It will be used by the Geological Survey of Victoria (GSV) to help build a publicly available, digital three-dimensional (3D) geological model to increase understanding of the region’s geology and to present this information visually.
The new data will complement existing data from previous surveys in the region and help build an understanding of how eastern Victoria has evolved over time.
Yes. The Geological Survey has safely carried out deep seismic reflection surveys using the same techniques across all of Victoria, including central and western Victoria in 2006 and 2009 respectively, to help build up an understanding of how the geology of Victoria has evolved over time.
This survey was conducted to improve scientists’ understanding of the geology of the region and of how it has evolved over time.
The technique cannot directly detect minerals. Minerals are known in the region and the results of the survey may potentially provide context for how these minerals have formed over time.
No. This survey was carried out to better understand the geology of eastern Victoria (and southeast Australia) and how it has evolved over time.
The area to be surveyed is not prospective for oil and gas. The survey has nothing to do with fracking.
The results of this survey will be publicly available through Geoscience Australia’s website and through the Geological Survey of Victoria (GSV).
Page last updated: 30 May 2019