The aim of this document is to: * outline the general process adopted by Geoscience Australia in modelling tsunami inundation for a range of projects conducted in collaboration with Australian and State Government emergency management agencies * allow discoverability of all data used to generate the products for the collaborative projects as well as internal activities.

The subsurface of the Earth is a complex system, one that we are yet to fully understand and model. It is hence impossible to automate the process of mapping and modelling, and the input of user experience and knowledge ('prior knowledge') is required to produce meaningful and useful outputs. This form of solution does not lend itself to a simple programmatic approach. However, by taking advantage of advances in computer technology and the application of numerical methods for modeling complex environments, we can do much to improve upon past results. Introduction As Australia's national geoscience organisation, Geoscience Australia (GA) plays an important role in the creation and delivery of fundamental geoscientific information. Studies are carried out at a wide range of scales, from a continental perspective to highly detailed local site investigations. In most situations, direct geological observations are supplemented by the inferences that can be made from geophysical measurements. Observations of the Earth's gravity and magnetic fields contain signals from subsurface materials, and extensive holdings of these measurements are commonly used to help create 3D subsurface models. With sparse hard constraints and incomplete, insufficient, noisy observations, knowledge workers or experts continue to play an important role in providing implicit prior constraints on any system to model this volume. The interface to these people becomes an important part of any set of tools for performing geological modeling of gravity and magnetic data. Users constantly demand a better experience and better outcomes when modeling the subsurface. Some of their recurring requests are for: * A simpler, more intuitive user-experience * Higher resolution * Models with larger extents * Faster processing * Inclusion of a greater number of geological and rock property constraints * Estimates of the uncertainty in the outcomes * Improved 3D visualisation * Tracking of input provenance and subsequent processing that is carried out * Organised management of 3D models Integration of the elements is a key consideration when developing solutions, as users are loathe to adopt procedures that become more involved and more difficult to understand and to piece together. Today, developments to produce world-class solutions typically take place across multiple agencies, involving many people, and at locations spread around the globe. This in itself is a challenge! We have focused our efforts on the following: * The management and delivery of rock properties * Spherical and Cartesian coordinate gravity and magnetic modelling software * Use of High Performance Computing (HPC) facilities * Use of a virtual globe application for 3D visualisation

In response to the devastating Indian Ocean Tsunami (IOT) that occurred on the 26th of December 2004, Geoscience Australia developed a framework for tsunami risk modelling. The outputs from this methodology have been used by emergency managers throughout Australia. For GA to be confident in the information that is being provided to the various stakeholders' validation of the model and methodology is required. While the huge loss of life from the tsunami was tragic, the IOT did provide a unique opportunity to record the impact of a tsunami on the coast of Western Australia. Eight months after the tsunami a post-disaster survey was conducted at various locations along the coast and maximum run-up was determined from direct observational evidence or anecdotal accounts. In addition tide gauges located in harbours along the coast also recorded the tsunami and provide a timeseries account of the wave heights and frequency of the event. This study employs the tsunami hazard modelling methodology used by Geoscience Australia (GA) to simulate a tsunami scenario based on the source parameters obtained from the Boxing Day earthquake of 2004. The model results are compared to observational evidence from satellite altimetry, inundation surveys and tide gauge data for Geraldton, a community on the Western Australian coast. Results show that the tsunami model provides good estimates of the wave height in deep water and also run up in inundated areas and it importantly matches the timing of the first wave arrivals. However the model fails to reproduce the timeseries data of wave heights observed by a tide gauge in Geraldton harbour. The model does however replicate the occurrence of a late arriving (16 hrs after first arrival) wave packet of high frequency waves. This observation is encouraging since this particular wave packet has been noted elsewhere in the Indian Ocean and caused havoc in harbours many hours after the initial waves had arrived and dissipated.

Basins on the western margin of Australia are both well explored (e.g. North West Shelf) or under-explored frontier basins (e.g. Perth Basin). For many of these basins, knowledge of basement and crustal structure is limited. To provide new insight into these fundamental features of a continental margin, we present the results of process-oriented gravity modelling applied to basins both with (North West Shelf) and without (Perth Basin) constraints on crustal structure. Process-oriented gravity modelling is a method that considers the rifting, sedimentation and magmatic processes that led to the present-day gravity field. By back-stripping the sediment load under different assumptions of isostasy (i.e. range of flexural rigidities), rift-related crustal structure can be inferred. When the rift and sedimentation gravity anomalies are combined and compared to observed free-air gravity, insight into the presence of magmatic underplating, the location of the continent-ocean boundary and the thermal history of a margin can, amongst other factors, be gained. Initial modelling suggests that the Perth Basin maintained a relatively low flexural rigidity throughout its history (effective elastic thickness ~5 km), which may reflect the prevalence of transtensional deformation during Late Jurassic-Early Cretaceous break-up between Australia and Greater India. However, constraining elastic thickness in the Perth Basin is made difficult by uncertainties in resolving the total sediment thickness (particularly in outboard parts of the basin) and crustal structure. Such uncertainties are less of an issue for some North West Shelf basins where seismic refraction data enhance the interpretation of abundant seismic reflection data.

A regional scale 3D geological map of the upper crustal sequence in the West Arnhem Land region, Northern Territory, was compiled from surface mapping, limited drilling information, and liberal amounts of geological inference. Modelling of the gravity and magnetic field response of this map was proposed as a means of evaluating the viability of this geological hypothesis. A relatively good supply of mass density and magnetic property data were available to constrain the transformation of 3D geological maps into property models in preparation for potential field modelling. The presence of numerous relatively thin magnetic horizons, dykes, and sills provided many challenges for producing geologically-realistic magnetic property models at a regional scale. Modelling of the gravity field at this scale was far more straight forward and successful. A stochastic procedure was used to derive a large number of geological maps by making small changes to the highly uncertain interpretive parts of the original 3D geological map. A subset of these derived geological maps had associated mass density models that could adequately reproduce the gravity field observations. The common characteristics of the geological models in this subset were isolated using statistical techniques and used to refine our portrayal of the regional scale 3D geological features.

No abstract available

Geoscience Australia collects and manages large amounts of data for Australia's marine zone, including bathymetry data and the legal boundaries of petroleum acreage release areas. Communicating this information to non-specialists can be difficult. To overcome this communication problem Geoscience Australia uses innovative visualisation techniques, including 3D flythroughs and video editing, to integrate raster and vector geospatial data into enhanced multimedia products. Geoscience Australia has used these techniques for a number of years and the resulting products are highly regarded by stakeholders interested in marine zone management and petroleum exploration. This paper examines four case studies where these innovative techniques were used to effectively communicate marine zone information with a wide audience.

In August 2002 the Council of Australian Governments (COAG) published a review of natural disaster relief and mitigation arrangements in Australia (COAG, 2003). One of the recommendations from this review included a commitment by COAG to develop and implement a five-year national program of systematic and rigorous disaster risk assessments. In response to this commitment, Geoscience Australia has undertaken a series of national risk assessments for a range of natural hazards including severe wind. This study includes four case studies representing different wind regions Perth (Region A), Brisbane (Region B), Gold Coast (Region B) and Cairns (Region C) to estimate the wind risk. Severe wind is one of the major natural hazards in Australia. These severe winds are chiefly produced by cyclones in the north and cold fronts or thunderstorms in the south. Geoscience Australia has developed a national wind hazard model for estimating the risk posed by peak wind gusts. In this study, the regional return period wind gusts used were as defined in the Australian/New Zealand wind loading standard (AS/NZS 1170.2, 2002) and applied the methodology detailed in the standard. The impact of severe wind varies considerably between structures at various locations, due to the geographic terrain, the height of the structure concerned, the surrounding structures and topographic factors. The wind multipliers defined in the AS/NZS 1170.2 can numerically describe the site wind exposure and speed modifications. These multipliers give quantitative measures of local wind conditions relative to the regional wind speed (defined as open terrain at 10 metre height) at each location. There are three local wind multipliers named terrain/height multiplier (Mz), shielding multiplier (Ms) and topographic (also called hill-shape) multiplier (Mh) influence the regional wind speed. The developed model estimates these multipliers using remote sensing and spatial information. The directional multiplier (Md) is considered from the standards determines the wind direction The relationship between the regional wind speed (VR) in open terrain at 10 metre height, the maximum local (site) wind speed (Vsite) and the local wind multipliers is: Vsite = VR × Md ×Mz × Ms × Mh The wind loading standard is known to be conservative in its approach to shielding by buildings upwind in a "shielding zone", and also with regard to the topographic shielding of structures. A number of modifications were made to remove the conservatism associated with AS/NZS 1170.2. The link between incident wind speed and loss is the structural vulnerability and contents loss model. For this study the models developed by George Walker for North Queensland structures using insurance loss data form two cyclone events have been used after validation. Damage levels across each region were assessed for various return periods (50-, 100-, 200-, 500-, 1000-, 2000- year). Severe wind damage losses were determined for each return period hazard level. Each city data set was regressed to obtain a corresponding Probable Maximum Loss (PML) curve. Finally the regression curves were used to determine annualised losses for each study area. The annualised percentage losses were estimated for Perth (0.0039), Brisbane (0.021), Gold Coast (0.04) and Cairns (0.137). In addition, spatially variable regional wind speeds for Perth region were estimated using eight weather stations data and linear interpolation techniques. The wind damage estimated using these wind speeds is significantly higher than the estimated from single station based wind speeds of AS/NZS 1170.2.

A holistic inversion algorithm has been developed for time-domain airborne electromagnetic (AEM) data. The algorithm simultaneously recovers a layered earth conductivity structure as well as unmeasured elements of the system geometry. It inverts a complete flight line of data in one inversion. This allows us to take advantage of the expected along-line continuity of conductivity and system geometry, which cannot be exploited when each sample is inverted independently. The conductivity and thickness of each layer and geometry variable is parameterised by the node coefficients of separate cubic-spline basis functions, which implicitly represent smooth continuous along line variations. Each of the cubic splines may have different node spacings that are chosen to adequately represent the expected scale length of lateral variability of conductivity and system geometry. The regularised inversion scheme is formulated to minimise an objective function comprised of data misfit, reference model misfit, and vertical and horizontal roughness terms. The minimisation is implemented via a gradient-based iterative scheme in which a sparse linearised system is solved by the conjugate gradient method within each iteration. The method has been applied to fixed-wing and helicopter AEM data. The results demonstrate that the method produces conductivity models that are geologically credible and consistent with downhole conductivity logs. They also show improved continuity and interpretability in comparison to sample by sample inversions. We found that the estimation of transmitter-receiver separation and receiver pitch geometry parameters was stabilised by the implicit along line continuity constraints.

The GA record contains abstracts of the contributions given at the "Geologically realistic inversion of gravity and magnetic data" workshop, held in Melbourne on 1 July 2006 as a prelude to the Australian Earth Sciences Convention 2006 (AESC 2006). The accompanying CD-ROM contains the abstracts given at the workshop in PDF format.