Geophysics

Geophysical methods are applied at all scales from the study of the behaviour core samples through to the entire earth. Our global geophysics efforts are oriented towards integrating observations with models of plate tectonics and mantle convection, which in turn are tied to basin-scale problems and resource exploration. This allows the analysis of the tectonic and sedimentary history of basins and continental margins, and in particular the modelling of crustal palaeo-stress fields of the Indo-Australian Plate. Results are linked to stratigraphy and fault analysis from seismic data. At the scale of mining operations, our geophysical research is focussed on assessing the in-situ state of ore bodies and the ground response to mining.

Global geophysics

Flooding of Australia

The group's research on the geological history of the global ocean basins is based on a unifying approach, investigating interactions between the Earth's mantle, crust, sediments and the oceans, including the modelling of long-term sea level change. The group is also involved in modelling the poorly explored evolution of the Antarctic Circumpolar Current (ACC) and Australia's palaeo-environments during the last 40 million years, using a coupled climate model (CCM) of atmosphere, land, ice and ocean. This will allow an exploration of the effects of the opening/closing of oceanic gateways on climate, ocean currents, carbon dioxide budget and biodiversity. EarthByte's resource exploration interests are aimed at oil and gas exploration in a basin analysis context. The group is involved in the modelling of palaeo-stress fields of the Indo-Australian Plate, linked to stratigraphy and fault analysis from seismic data, and tying basin-scale observations to models of mantle convection and lithospheric deformation.

The image above is an application example for linking plate tectonics with evolution of continental flooding via geodynamic modelling. In the Early Cretaceous (top figure), 130 million years ago Australia is bordered by a deep oceanic trench in the east, where an oceanic plate is being recycled (subducted) back into the Earth’s mantle. The next figure shows that between 130 and 80 million years ago, the Australian plate moved east, overriding the sinking plate to the east. As a consequence, eastern Australia is drawn down by the sinking slab, resulting in marine inundation of large parts of eastern Australia by a shallow sea. After 80 million years ago, the downward drag of the subducting plate on the surface slowly diminished due to the increasing vertical distance between the sinking slab and the continent, resulting in a rebound and uplift of eastern Australia. About 45 million years ago, Australia started moving north, resulting in convergence with Indonesia. The entire continent is now drawn down once again (bottom figure), caused by a system of subducting slabs around Indonesia and Papua New Guinea, which Australia is approaching. For further information contact A/Prof. Dietmar Müller.

Mining Geophysics

Our research in mining geophysics is undertaken through associations with CRC Mining and the Australian Centre for Field Robotics. For mining problems, the geophysical methods of most use are borehole logging, seismic reflection surveying, microseismic monitoring and electromagnetic imaging using radar. These allow detailed maps of the subsurface geology to be produced and the geotechnical properties of the subsurface to be inferred. Mining increasingly requires high calibre geotechnical information so that the response of the ground to mining can be predicted and controlled.

Areas of active research interest include 3D seismic reflection surveying, inversion of seismic reflection results, analysis of geophysical borehole logs to provide geological and geotechnical models, borehole radar surveying in support of reef mining in hard rock environments, data fusion, geological sensing in support of mine automation and regional scale 3D modelling of the ground response to mining.

Seismic

Geoinformatics

AuScope is a research infrastructure development project aimed at unravelling the structure and evolution of the Australian continent. The School of Geosciences participates in AuScope infrastructure development through the EarthByte project. Earth processes over geological timescales, such as sea level fluctuations and paleo-topography, cannot be understood outside of a plate tectonic context. The EarthByte group is developing a Palaeo-Geographic Information System that is centered on the open source and architecture-independent GPlates software, and XML-based service interfaces and databases. EarthByte is developing open source and cross-platform computational solutions for applied and fundamental paleogeographic problems that will link GIS data bases to plate motions, palaeogeography and geodynamics modelling packages. This system is designed to create the foundation for an e-geoscience framework by linking geological and geophysical observations to process modelling tools. For further information contact A/Prof. Dietmar Müller.

Present Australia