Airborne Gravity Survey
An airborne gravity survey has been conducted as part of The CarbonNet Project to provide a better understanding of the onshore, nearshore and immediate offshore geology of the Gippsland Basin. The Gippsland Basin Nearshore Airborne Gravity survey was conducted by Sander Geophysics Ltd. on behalf of the Department of Primary Industries from 23 November to 11 December 2011. This project received funding from the Australian Government as part of the Clean Energy Initiative.
The precise instrumentation used during an airborne gravity survey can measure subtle differences in the force of gravity. The different physical characteristics of rock types below the earth’s surface cause variations in the gravity field, with denser rocks producing a stronger gravity field. The instrumentation can also provide data that enables CarbonNet’s geoscience experts to assess the structure and composition of the rocks in the region.
During the Gippsland Basin nearshore airborne gravity survey, the magnitude of the gravity field was measured along 10,523 kilometres of lines flown in a northeast – southwest orientation. These lines were one kilometre apart, with some additional infill lines along the coast flown with 500 metre spacing.
Survey resultsThe Gippsland gravity survey was conducted across the onshore, nearshore and immediate offshore region outlined in the map above. The data collected overlaps with existing onshore gravity data, providing a seamless overview of the region’s geology.
The data collected are displayed in the map where the blue-magenta colours represent low gravity values and the orange-red colours represent high gravity values.
The map shows that there are areas of less gravity response in the southwest than the gravity response in the north. These differences are only measurable with very sensitive research equipment. This indicates that the rocks in the northern part of the survey area are relatively denser than the rocks in the southwest of the survey area. There are also local changes in gravity responses throughout the survey area that can be interpreted as geological boundaries, changes in thickness of geological units and faults in the underlying geology.
What was the purpose of the survey?
Gravity data are commonly used for mineral or petroleum exploration. In this case the data are a valuable component of the information used to build detailed 3D geological models of subsurface rock structure. These models assist the CarbonNet experts to identify and assess potential carbon storage sites.
To download the report and data from this survey visit the DPI Earth resources online store.
If you have any queries please email CarbonNet.Info@dpi.vic.gov.au