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  • Australia's North West Margin (NWAM) is segmented into four discrete basins which have distinct rift and reactivation histories: Carnarvon, offshore Canning (Roebuck), Browse and Bonaparte. Bonaparte Basin incorporates Vulcan and Petrel sub-basins. The Bonaparte Basin stands out as an extensive sedimentary basin which has a geological history spanning almost the entire Phanerozoic, with up to 20 km of sediment accumulation in the centre. Browse Basin has considerably less thick sediment accumulation ? 12 km at maximum, which is still high for general hydrocarbon potential estimation. The structural architecture of the region is the product of a number of major tectonic events, including: ? Late Devonian northeast-southwest extension in the Petrel Sub-basin; ? Late Carboniferous northwest-southeast extension in the proto-Malita Graben, Browse Basin and proto-Vulcan Sub-basin; ? Late Triassic north-south compression; ? Early-Mid Jurassic development of major depocentres in the Exmouth, Barrow and Dampier sub-basins, and extension in the Browse Basin; ? Mid-Late Jurassic breakup in the Argo Abyssal Plain, onset of thermal sag in the Browse basin and extension in the Bonaparte Basin; ? Valanginian breakup in the Gascoyne and Cuvier abyssal plains, and onset of thermal sag in the Bonaparte Basin; and ? Late Miocene reactivation and flexural downwarp of the Timor Trough and Cartier Sub-basin Many of these events have involved processes of lower crustal extension and are strongly controlled by the pre-existing regional structural fabrics and basement character. Most reliable information on basement and deep crustal structure in the region comes from combined ocean-bottom seismograph (OBS) and deep reflection profiling along several regional transects (including Vulcan and Petrel transects in the Bonaparte Basin, and one transect in the Browse Basin). Average spacing between the OBSs of 30 km and shot spacing of 100 m with data recording to maximum offsets of 300 km enabled development of accurate crustal-scale seismic velocity models. Deep reflection data along the coincident profiles were recorded as part of Geoscience Australia?s regional grid of seismic lines. Consistent interpretation of several key horizons tied to petroleum exploration wells through the entire grid created the basis for co-interpretation of the OBS and deep reflection data supplemented by gravity field modelling.

  • The discovery of commercial oil in the Cliff Head-1 well in 2001 set an important milestone in the exploration history of the offshore northern Perth Basin. The region had been largely underexplored before then, partly due to the perception that the Hovea Member, a 10 to 40 m-thick unit straddling the Permian-Triassic boundary (PTB) and recognized as the main source of onshore petroleum accumulations, was not developed offshore (Crostella, 2001). The typing of the Cliff Head oil to the Hovea Member provided evidence that the key onshore petroleum system extends offshore and revitalized exploration in the area with 13 new field wildcat wells drilled since 2002. Three discoveries have been made subsequently further offshore in the Abrolhos Sub-basin with gas retrieved in Frankland-1 and Perseverance-1 and oil and gas in Dunsborough-1. A review of source rock and oil geochemical data was undertaken by Geoscience Australia in the offshore northern Perth Basin as part of a major integrated study aimed at reassessing the basin's prospectivity. This work supports the release of offshore exploration areas W13-19 and W13-20, two major blocks straddling the Houtman and Abrolhos Sub-basins with small portions extending into the Zeewyck and Gascoyne Sub-basins (Fig. 1). Well control is provided by 5 wells from the Wittecarra Terrace in the northern Abrolhos Sub-basin and Houtman-1 in the Houtman Sub-basin.

  • Poster for presentation at European Space Agency 'Fringe' conference, 23-27 March 2015.

  • Abstract for IGNSS 2015 conference: A Global Navigation Satellite System (GNSS) antenna calibration facility has been established at Geoscience Australia, for determining individual antenna calibrations as well as aiding the establishment of typemean calibrations as used by the International GNSS Service (IGS). Studies have highlighted the importance of accounting for the variation in individual antenna calibrations for high precision positioning applications. In order to use individual antenna calibrations reliably, the repeatability of the calibration needs to be well understood. In this paper, we give an overview of the repeatability of calibrations for different antenna types. We also present a case study on the application of an individual GNSS antenna calibration in Australia and its effect upon positioning.

  • The Prompt Assessment of Global Earthquakes for Response (PAGER) System plays a primary alerting role for global earthquake disasters as part of the U.S. Geological Surveys (USGS) response protocol. PAGER monitors the USGSs near real-time U.S. and global earthquake origins and automatically identifies events that are of societal importance, well in advance of ground-truth or news accounts. Current PAGER notifications and Web pages estimate the population exposed to each seismic intensity level. In addition to being a useful indicator of potential impact, PAGERs intensity/exposure display provides a new standard in the dissemination of rapid earthquake information. This paper provides an overview of the PAGER system, both of its current capabilities and ongoing research and development. Specifically, this paper summarises the underpinning models and datasets developed to improve PAGER exposure and impact modules. These include: global site-response models, enhanced earthquake source and loss databases, the Atlas of ShakeMaps and population exposure catalogue, and a global building inventory. The use of these methods and databases are demonstrated using the USGSs response to the 12 May 2008 Wenchuan, China, earthquake. Finally, we comment on the potential use of PAGER tools and databases for improved near real-time earthquake alerting in Australia.

  • Geoscience Australia is currently undertaking the process to update the Australian National Earthquake Hazard Map using modern methods and an extended, more complete catalogue of Australian earthquakes. This map is a key component of Australia's earthquake loading code. The characterisation of strong ground-shaking using Ground-Motion Prediction Equations (GMPEs) underpins any earthquake hazard assessment. Recently there have been many advances in ground-motion modelling for active tectonic regions. However, the challenge for Australia - as it is for other stable continental regions - is that there are very few ground-motion recordings from large-magnitude earthquakes with which to develop empirically-based GMPEs. Consequently, there is a need to consider other numerical techniques to develop GMPEs in the absence of recorded data. Recently published Australian-specific GMPEs, which employ these numerical techniques, are now available and these will be integrated into Geoscience Australia's future hazard outputs. <p> This paper addresses several fundamental aspects related to ground-motion in Australia that are necessary to consider in the update of the National Earthquake Hazard Map, including: 1) a summary of recent advances in ground-motion modelling in Australia; 2) a comparison of Australian GMPEs against those commonly used in other stable continental regions; and 3) the impact of updated attenuation factors on local magnitudes in Australia. Specific regional and temporal aspects of magnitude calculation techniques across Australia and its affects on the earthquake catalogue will also be addressed. </p>

  • As part of the Australian Government National CO2 Infrastructure Plan (NCIP), Geoscience Australia is undertaking CO2 storage assessment of the Vlaming Sub-basin located offshore Western Australia in the southern Perth Basin. The Vlaming Sub-basin is a Mesozoic depocentre containing up to 14 km of sediments. Close proximity of the basin to industrial polluters in the Perth area dictates the need to find CO2 storage solutions in this basin. The main reservoir unit identified as suitable for storage of CO2 is the Early Cretaceous Gage Sandstone deposited in paleo-topographic lows of the Valanginian breakup unconformity. The reservoir unit is laterally extensive (over 1,500 km2) and over most of the area reasonably thick (100 - 300 m). It lies at depths between 1400 and 2000 m below the seafloor, which is suitable for injection of the supercritical CO2 and makes it an attractive target for the long-term storage. The reservoir unit is overlain by a thick deltaic to shallow marine succession of the South Perth Shale, which represents a regional seal in the area. Carbon Storage taskforce estimated that up 1 GT of CO2 can be stored in the Gage Sandstone. The first assessment of the Vlaming Sub-basin undertaken by CO2CRC focused on evaluation of the reservoir unit and overall storage capacity. The current study is based on interpretation and integration of the seismic, well and marine datasets, both existing and acquired since the previous assessment. It includes detailed analysis of reservoir and seal properties and a comprehensive evaluation of the seal integrity risks to allow a more accurate and realistic modeling for CO2 storage.

  • The Vulcan Sub-basin has been actively explored for over twenty years, with oil production from the Jabiru and Challis-Cassini fields, and the depleted Skua Field, all of which were sourced by the Upper Jurassic Lower Vulcan Formation within the Swan Graben. The need to discover other oil-prone petroleum systems led to this study focussing on oils that have a different composition to those of the aforementioned oils. Geochemical analyses (bulk and compound-specific isotopes, GC and GC-MS of saturated and aromatic hydrocarbons) have characterised the Vulcan Sub-basin oils and condensates into three families (Fig 1); a marine oil family (with some terrigenous influence) comprising Jabiru, Challis, Skua, Talbot and Tenacious; a terrestrially-influenced oil family comprising Maret, Montara, Padthaway and Bilyara which have more varied geochemistry; and, a family of condensates from Tahbilk, Swan and Eclipse. The composition of these condensates is more reflective of reservoir alteration effects (such as leakage and gas flushing) than the type of organic matter in their source rocks. The terrestrially-influenced oil family is located in the southernmost part of the Vulcan Sub-basin and in the northern Browse Basin, most probably having being source from the Lower-Middle Jurassic Plover Formation. The Plover Formation contains liquid-prone source rocks within the Skua Trough, albeit immature for hydrocarbon generation. Similar source rocks are believed to occur beneath the Swan and Paqualin grabens since oils with mixed composition are found at Puffin, Pituri and Oliver.

  • Recent events in Queensland in 2011 and 2013 have highlighted the vulnerability of housing to flooding and have caused billions of dollars in losses. To reduce future losses there is a significant need for mitigating the risk posed by existing residential buildings in flood prone areas. Therefore, a project is underway within the new Bushfire and Natural Hazards Cooperative Research Centre (BNHCRC) to provide an evidence base to inform decision making on the mitigation of flood risk by providing information on the cost-effectiveness of a range of mitigation strategies. As an initial step to assess mitigation options, after conducting a review of existing schemas, a new building schema is developed to categorise the Australian residential buildings into a limited number of typical building types for which vulnerability functions can be developed. The proposed schema divides each building into the sub-elements of foundations, bottom floor, upper floors (if any) and roof of the building to describe its vulnerability. The schema classifies each building floor based on the attributes of Construction Period, Fit-out Quality, Storey Height, Floor System, Internal Wall Material and External Wall Material. The schema defines 60 discrete building/vulnerability classes based on the above mentioned attributes. It excludes combinations that are invalid in an Australian context. Furthermore, the schema proposes 6 roof types based on material and pitch of the roof.