A seismic survey was conducted across southeastern Australia during March to April 2018. It was done by Geoscience Australia, Geological Survey of New South Wales, Geological Survey of Victoria and AuScope Limited.

What is the purpose of the survey?

This survey has collected information about the deep crust of Earth, such as the orientation of major faults. It will help geologists to understand the geology up to 40 km below the surface and will assist government to make decisions about:

  • geohazards (earthquakes and landslides)
  • groundwater and geological resources
  • infrastructure location.

Where did the survey take place?

The survey was designed to fill a gap in information about southeastern Australia. It was conducted from west to east to collect data about the faults and crustal boundaries, which are mostly oriented north to south.

As there are no continuous straight roads in the area, the survey was split into three lines:

  • south of Benalla to Tom Groggin (VIC)
  • north of Benambra (VIC) to south of Bonang (VIC)
  • southwest of Bonang to south of Eden (NSW)

Location of the Southeast Lachlan Crustal Transect seismic survey (red lines)

Location of the Southeast Lachlan Crustal Transect seismic survey (red lines).

What is involved in a seismic survey?

A deep crustal seismic survey requires surveyors, three large vibroseis trucks, a control truck, smaller utes (to transport instruments and people) and about 30 km of sensors.

The survey mostly followed the verge of existing roads and tracks. Some sections went through private land, with the landholder's consent. Surveyors marked the route of the seismic survey with biodegradable blue spray paint.

Hundreds of sensors, called geophones, were placed off the edge of the road along the surveyor's line. The geophones record all the data.

Small pressure (or seismic) waves were generated by the vibroseis trucks at the centre of the line of geophones. These waves travelled into the ground, were reflected by geological features and then measured by the geophones at the surface. After each reading, the geophones at the end of the line were repositioned to the front of the line. The trucks then moved to the new centre location and repeat the process. Between eight and 15 km was surveyed in a day.

More information

For more information about seismic surveys

Additional gravity survey

Gravity readings will be measured along the seismic line in May 2019. Gravity data is used to determine crustal thickness and density, and will be used with the seismic data to help understand the rocks below the surface.

The gravity survey will take precise location (using GPS) and gravity measurements at 400 m intervals. The reading is taken by placing a small instrument on the ground, levelling it and recording Earth's gravitational pull. Each reading takes about three to five minutes to collect.

Gravity measurements along Line 1 will extend further east than the seismic survey. The extended line will pass through Jindabyne and Cooma.

Map of proposed gravity measurement sites

Map of proposed gravity measurement sites.

Operator taking a gravity reading

Operator taking a gravity reading.

Additional magnetotelluric survey

A magnetotelluric survey will be undertaken along the seismic line between September and November 2019. Magnetotelluric data is used to determine the nature of the deep crust and will be used with the seismic data to help understand the geology below the surface.

The survey will measure Earth’s natural electrical properties at 4 km intervals. Measurements are taken by placing a small array of sensors in and on the ground. Each measurement takes about 24 hours to collect. The survey is expected to take about three weeks to complete.

Magnetotelluric measurements along Line 1 will extend further east than the seismic survey.

Map of proposed magnetitelluric survey sites

Map of proposed magnetotelluric survey sites.

Magnetotelluric survey equipment being used in the field (image courtesy of Geoscience Australia).

Magnetotelluric survey equipment being used in the field (image courtesy of Geoscience Australia).

Data release

The data collected must be processed and interpreted before it will be made available to the public some time in 2019.

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