The Southwest Margin is a section of the continental margin off Australia's western coast. It includes the Paleozoic to Mesozoic Southern Carnarvon, Perth and Mentelle basins, as well as the Naturaliste and Wallaby plateaus. While several smaller hydrocarbon discoveries have been made onshore, the offshore region remains under explored. Recent studies, however, indicate there is potential for new petroleum discoveries in many of these frontier areas (e.g. Nicholson et al., 2008; Borissova et al., 2010; Jones et al., 2011). Despite the new geological insights gained from these studies, depth-to-basement and basement structure and composition beneath the Southwest Margin sedimentary basins remain poorly understood. The extent of exposed basement outcrop is limited, only a few wells intersect basement and, in many areas the basement horizon cannot be resolved using seismic data. An understanding of basement is however important when conducting basin studies, as the basement of any basin provides the foundation onto which sediment fill is deposited. As tectonic stresses are applied to a region, the rheology and mechanical behaviour of the basement influences how the crust deforms. Hence variations in basement strength, composition and structure significantly influence the resulting basin geometry, patterns of sediment deposition and basement derived heat flow. All of these factors fundamentally affect the generation and preservation of hydrocarbon resources. Geoscience Australia is currently engaged in a study to improve our understanding of the basement in the Southwest Margin region, which will generate the following products: - regional gravity and magnetic datasets - a map of interpreted basement terrane distribution - maps of interpreted basement composition and structure - a depth-to-basement model. This work develops alternative technical methodologies to define the basement architecture so it can be used as a framework for predictive basin analysis where other datasets are unavailable. Although this study will primarily complement offshore petroleum exploration studies along a rifted margin; the methodologies described here are applicable to other exploration activities in many different geographic and tectonic settings.

Abstract

We report on an assessment of severe wind hazard across the Australian continent, and severe wind risk to residential houses (quantified in terms of annualised loss). A computational framework has been developed to quantify both the wind hazard and risk due to severe winds, based on innovative modelling techniques and application of the National Exposure Information System (NEXIS). A combination of tropical cyclone, synoptic and thunderstorm wind hazard estimates is used to provide a revised estimate of the severe wind hazard across Australia. The hazard modelling utilises both 'current-climate' information and also simulations forced by IPCC SRES climate change scenarios, which have been employed to determine how the wind hazard will be influenced by climate change. We have also undertaken a national assessment of localised wind speed modifiers including topography, terrain and the built environment (shielding). It is important to account for these effects in assessment of risk as it is the local wind speed that causes damage to structures. The effects of the wind speed modifiers are incorporated through a statistical modification of the regional wind speed. The results from this current climate hazard assessment are compared with the hazard based on the existing understanding as specified in the Australian/New Zealand Wind Loading Standard (AS/NZS 1170.2, 2002). Our analysis has identified regions where the design wind speed depicted in AS/NZS 1170.2 is significantly lower than 'new' hazard analysis. These are regions requiring more immediate attention regarding the development of adaptation options including consideration by the wind loading standards committee for detailed study in the context of the minimum design standards in the current building code regulations.

Two significant offshore data acquisition surveys along Western Australia's continental margin (AusGeo News 92) were recently completed by Geoscience Australia. They form part of the agency's ongoing collection of fundamental pre-competitive data and information to understand Australia's offshore frontier basins, and assist with planning and management of Australia's marine environments.

Contained in: Proceedings of papers presented at an industry workshop held in Perth, 20 June 2002. Edited by K.F. Cassidy (See link)

Contained in: Proceedings of papers presented at an industry workshop held in Perth, 20 June 2002. Edited by K.F. Cassidy (See link)

Contained in: Proceedings of papers presented at an industry workshop held in Perth, 20 June 2002. Edited by K.F. Cassidy (See link)

Contained in: Proceedings of papers presented at an industry workshop held in Perth, 20 June 2002. Edited by K.F. Cassidy (See link)

Contained in: Proceedings of papers presented at an industry workshop held in Perth, 20 June 2002. Edited by K.F. Cassidy (See link)

Contained in: Proceedings of papers presented at an industry workshop held in Perth, 20 June 2002. Edited by K.F. Cassidy (See link)