Continental Australia is characterised overall by relatively high levels of seismic activity in comparison with intracratonic areas worldwide. However, the link between earthquake events and earthquake-related geomorphology in Australia remains poorly understood for all except the largest events, because landscape impact unambiguously attributable to seismic activity is typically difficult to recognise. In this context, we describe several unusual fracture systems of possible tectonic origin that transect granite pavements in the Archaean eastern Pilbara Craton of Western Australia. Occurring at four localities (Gallery Hill, North Shaw, Mulgandinnah Hill and Muccan) separated by up to 150 km, the fracture systems typically range up to 100 m in length and 20 m in width, locally offset pavement surfaces by up to 15 cm vertically, and expose uniformly fresh-looking rock. At one locality (Muccan), the fractures directly crosscut two generations of aboriginal petroglyphs etched into the pavement surface, which suggests that fracture formation occurred relatively recently, and probably quite rapidly. All four localities are characterised by extensional structures (tension fractures and dilated joints) striking 020?040?, and three preserve compressional structures (steeply-dipping reverse faults at Gallery Hill and North Shaw, A-tent crestal fractures at Mulgandinnah Hill) trending 100?135?. These strongly correlated alignments militate against an origin controlled purely by weathering-related phenomena, and the observed pattern is compatible with the formation of all documented fracture systems within a single East Pilbara-wide stress field, dominated by pure shear and characterised by NE?SW to NNE?SSW directed maximum horizontal compression. This orientation is consistent with that derived via spatial averaging of the stress orientation data available from northwestern Australia. The results are preliminary, but have exciting implications for: (1) inexpensive field-based determination of regional stress orientation, and (2) probabilistic seismic hazard assessment and the identification of earthquake-prone regions using granitic landforms.

Map showing the Geomorphic Features of the Australian Margin and Island Territories. The features were interpreted from Geoscience Australia's 250 m horizontal bathymetry model and other published data, and include those specified in the International Hydrographic Office definitions.

Geomorphic banks were mapped in this study based on a GIS analysis of a 100 m bathymetry grid for the Great Barrier Reef produced by Beaman (2010). The bathymetric data were contoured at 5 m intervals and used to interpret the location of geomorphic bank features, defined as having at least one steep (i.e. greater than ~2 degrees) slope rising more than 15 m above the level of surrounding seafloor. All banks were digitised by hand aided using three-dimensional imagery. Bank polygons were created in ArcGIS with the base of slope taken as the outer edge of the bank. Mean bank elevation estimates thus include the bank slopes as well as planar bank-tops. Only banks occurring on the continental shelf of the Great Barrier Reef between the 20 and 200 m isobaths, and between the latitudes of 10 to 25° S were included. Disclaimer: Geoscience Australia gives no warranty regarding the data downloads provided herein nor the data's accuracy, completeness, currency or suitability for any particular purpose. Geoscience Australia disclaims all other liability for all loss, damages, expense and costs incurred by any person as a result of relying on the information in the data downloads.

Measurements of water turbidity, currents, seafloor sediment samples and geophysical data document the sedimentary processes and the Late Quaternary sedimentary history of a continental shelf valley system on the East Antarctic continental margin.

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A geological investigation was carried out by the writer. The aim was to check the previous mapping of the geology, and if necessary, to assist the Magnetician in locating a suitable site for magnetic observations. Some aspects of geomorphology, and the reconnaissance survey work carried out are discussed in this report.

An examination of regionally extensive hill-shaded SRTM 90m resolution and DLI 10 m resolution digital elevation data and discussions with government and industry geologists familiar with the local geology has resulted in the identification of thirty eight previously unrecognised linear topographic scarps in the southwest and central west of Western Australia. I contend that most of these relate to Quaternary surface-rupturing earthquakes. If validated, this more than doubles the number of Quaternary fault scarps known from this area, bringing the total to sixty. The newly recognised scarps average between 25 km and 50 km in length and from ~1.5 m to 20 m in height. The geometric, recurrence and spatial attributes of these features makes it possible to propose a model describing the causative seismicity. The model contends that uniform contractional strain in the ductile lithosphere manifests as localised, transient and recurrent brittle deformation in zones of pre-existing crustal weakness in the upper lithosphere. The data presented allow for ready calculation of the maximum probable magnitude earthquake for the southwest of Western Australia, and identify 'earthquake prone' regions of interest to seismic hazard assessors.

Processes across the grounding zone are important in understanding the retreat behaviour of ice streams but are poorly understood because of the difficulty of accessing the region. The Antarctic Shelf preserves geomorphic features and sedimentary structures left by ice retreat which can provide insights into processes in and close to the grounding zone. Sidescan sonar records from Prydz Bay image a range of features that reflect changes in processes across the Amery Ice Shelf grounding zone during retreat after the Last Glacial Maximum. The presence of fluted and mega-scale glacial lineations indicates that the ice moved over an unfrozen, deforming bed in the zone up stream of the grounding zone. For most of the Amery Ice Shelf, the inter-flute dunes reflect strong thermohaline circulation in the ice shelf cavity. Sand and gravel recovered in cores from beneath the Amery Ice Shelf indicate significant current speeds, possibly enhanced by tidal pumping. The sea floor in the Lambert Deep on the western edge of the Amery Ice Shelf lacks inter-flute dunes and has a sea floor covered in subglacial features. Transverse steps cutting across flutes indicate the presence of subglacial cavities at the bed between patches of grounded ice as the ice approached the grounding zone. The presence of an esker indicates water flowing in a subglacial tunnel. The polygonal ridges are similar to those formed where surging glaciers have stagnated. This at least implies periods of stagnation before the ice flowing into the Lambert Deep retreated from successive grounding line positions.

A quantitative synthesis of the sedimentology and geomorphology of the South West Planning Region of Australia. Sediment data used was sourced from previous and new quantitative carbonate and grainsize data generated from surficial seabed sediment samples. All sample information and assays are available in the MARS database. The report and new assays were generated as part of an MOU with the Department of Environment and Heritage (National Oceans Office) and the results are reported in a format appropriate for use in regional marine planning.

This report describes the iterative methods used to create the seascapes, including a detailed appendix documenting the different datasets used in the different planning zones. Creating the seascapes is necessarily an iterative process whereby the available datasets are combined in different combinations, or added as they become available, using an unsupervised 'crisp' ISOClass classification in ERMapper. In each classification only biophysical properties that have consistent and definable relationships with the benthic biota and are known in sufficient detail across Australia's entire marine region are used to create the seascapes. An initial validation of the classification technique has been undertaken on a subset of the data for the shelf surrounding Tasmania using an alternative unsupervised 'fuzzy' classification. Results of this validation indicate that the unsupervised classification methodology provides consistent and reliable classes for defining the seascapes.