On 23 March 2012 a MW 5.4 intraplate earthquake occurred in the eastern Musgrave Ranges of north-central South Australia, near the community of Ernabella (Pukatja). This was the largest earthquake recorded on mainland Australia in the past 15 years and resulted in the formation of a 1.6 km-long surface deformation zone that included reverse fault scarps with a maximum vertical displacement of ~0.5 m (average ~0.1 m), extensive ground cracking, and numerous rock falls. Fifteen months later, on 09 June 2013 a MW 5.6 earthquake (the Mulga Park earthquake) occurred ~15-20 km northwest of the 2012 rupture. The P-axes of the focal mechanisms constructed for both events indicate northeast-oriented horizontal compressive stress. However, the focal mechanism for the Mulga Park earthquake suggests strike-slip failure, with a sub-vertical northerly-trending nodal plane favoured as the failure plane, in contrast to the thrust mechanism for the 2012 event. Despite being felt more widely than the 2012 event, ground cracking and minor dune settlement were the only surface expressions relating to the Mulga Park earthquake. No vertical displacements were evident, nor were patterns indicative of a significant lateral displacement. An 18 km long north to north east trending arcuate band of moderate to high cracking density was mapped parallel to the surface trace of the Woodroffe Thrust, a major crust-penetrating fault system. A lobe of high-density cracking ~5km long, coincident with the calculated epicentral location, extended to the north from the centre of the main arc. We speculate that the rupture progressed to the south beneath the northern high-density lobe (consistent with the dimensions expected from new scaling relations), and that the larger arcuate band of cracking might relate to positive interference resulting from reflection of energy from the Woodroffe Thrust interface. Both events provide new insight into the rupture behaviour of faults in non-extended cratonic crust.

We have developed models for the prediction of bedrock ground motion response spectra in several regions of Australia. In Eastern Australia, we developed models for the Paleozoic Lachlan Fold Belt, and the Sydney Basin that lies within it, and in Western Australia we developed models for the Yilgarn Craton and the adjacent Perth Basin. The models are based on the broadband simulation of accelerograms using regional crustal velocity models and earthquake source scaling relations. For both the Lachlan Fold Belt and Yilgarn regions, we used comparison of synthetic seismograms with the recorded seismograms of small earthquakes to test and modify regional crustal velocity models. In Western Australia, we used the rupture models of the 1968 Mw 6.6 Meckering earthquake and the 1988 Mw 6.25, 6.4 and 6.5 Tennant Creek earthquakes to constrain the scaling relationship between seismic moment and rupture area. Other aspects of the source scaling relations were derived from our scaling relations for earthquakes in eastern North America (Somerville et al., 2001). In eastern Australia, the data available for historical earthquakes are insufficient to constrain earthquake scaling relations, so we have used the relations for Western Australia as well as the relations for the western United States (Somerville et al., 1999). We generated suites of broadband ground motion time histories using these source scaling relations and crustal structure models. These ground motion simulations were used to generate ground motion prediction models for each region. The ground motion models have been compared with the model of Liang et al. (2008) for Western Australia, with models for Eastern North America including Atkinson and Boore (2006), Somerville et al (2001), and Toro et al (1997), and with the NGA models.

Effective disaster risk reduction is founded on knowledge of the underlying risk. While methods and tools for assessing risk from specific hazards or to individual assets are generally well developed, our ability to holistically assess risk to a community across a range of hazards and elements at risk remains limited. Developing a holistic view of risk requires interdisciplinary collaboration amongst a wide range of hazard scientists, engineers and social scientists, as well as engagement of a range of stakeholders. This paper explores these challenges and explores some of the common and contrasting issues sampled from a range of applications addressing earthquake, tsunami, volcano, severe wind, flood, and sea-level rise from projects in Australia, Indonesia and the Philippines. Key issues range from the availability of appropriate risk assessment tools and data, to the ability of communities to implement appropriate risk reduction measures. Quantifying risk requires information on the hazard, the exposure and the vulnerability. Often the knowledge of the hazard is reasonably well constrained, but exposure information (e.g., people and their assets) and measures of vulnerability (i.e., susceptibility to injury or damage) are inconsistent or unavailable. In order to fill these gaps, Geoscience Australia has developed computational models and tools which are open and freely available. As the knowledge gaps become smaller, the need is growing to go beyond the quantification of risk to the provision of tools to aid in selecting the most appropriate risk reduction strategies (e.g., evacuation plans, building retrofits, insurance, or land use) to build community resilience.

This isoseismal data shows the distribution of the shaking effects of earthquakes that were felt in Australia between 1841 and 2003. The data was captured from maps collated in the Geoscience Australia record "Atlas of Isoseismal Maps of Australian Earthquakes" compiled by K.F. McCue and supplimented with data from recent Centre for Earthquake Research Australia (CERA) reports and other unpublished data. Data present include felt values (points) and isoseismal contours (lines) from 405 earthquake events in an attributed GIS Dataset.

Mackay, in Central Queensland, lies about mid way between Brisbane and Cairns and with a resident population around 71,400. The Mackay urban area, which is the focus of this study, is home to around 59,000. This study makes extensive use of Geoscience Australia's Risk-GIS method, which is a fusion of the decision support capabilities of geographical information systems, or GIS and the philosophy of risk management. The analysis of risk involves assessing the levels of hazard at Mackay, developing an understanding of the vulnerability of the elements which are at risk within the community and synthesising a range of event scenarios. A comprehensive building database is used to generate damage assessments for the various scenarios with each suburb ranked for its contribution to overall community vulnerability and for exposure to the various hazards. These two rankings determine total risk for each suburb by hazard, which allows the overall community risk from the various hazards to be compared.

The Mount Lofty and Flinders Ranges of South Australia are bound on the east and the west by reverse faults that thrust Proterozoic and/or Cambrian basement rocks over Quaternary sediment. These faults range from a few tens to almost one hundred kilometres in length and tend to be spaced significantly less than a fault length apart. In the few instances where the thickness of overthrust sediment can be estimated, total neotectonic throws are in the order of 100-200 m. Slip rates on individual faults range from 0.02-0.17 mm/a, with one unconfirmed estimate as high as 0.7 mm/a. Taking into account the intermittent nature of faulting in Australia, it has been suggested that 30-50% of the present-day elevation of the Flinders and Mount Lofty Ranges relative to adjacent piedmonts has developed in the last 5 Ma. Uplifted last interglacial shorelines (ca. 120 ka) along the southern coastline of the Mount Lofty Ranges indicate that deformation is ongoing. Palaeoseismological investigations provide important insight into the characteristics of the large earthquakes responsible for deformation events. Single event displacements of 1.8 m have been measured on the Williamstown-Meadows Fault and the Alma Fault, with the former relating to a surface rupture length of a least 25 km. Further to the south in Adelaide's eastern suburbs, a 5 km section of scarp, potentially relating to a single event slip on the Eden-Burnside Fault, is preserved in ca. 120 ka sediments. Where the Eden-Burnside Fault meets the coast at Port Stanvac 20 kilometres south, the last interglacial shoreline is uplifted by 2 m relative to its expected position. At Normanville, on the uplifted side of the Willunga Fault, the last interglacial shoreline is over 10 m above its expected position, implying perhaps five or more surface rupturing events in the last ca. 120 ka on this >50 km long fault. On the eastern range front, a very large single event displacement of 7 m is inferred on the 54 km long Milendella Fault, and the 79 km long Encounter Fault displaces last interglacial shorelines by up to 11 m. There is abundant evidence for large surface-breaking earthquakes on many faults within 100 km of the Adelaide CBD. Slip rates are low by plate margin standards, implying a low rate of recurrence for M7+ events on individual faults (perhaps 10,000 years or more). However, a proximal moderate-sized event or even a large event at distance has the potential to cause significant damage to Adelaide, particularly given its construction types and local site conditions.

Legacy product - no abstract available

An assumption of probabilistic seismic hazard assessment is that within each source zone the random earthquakes of the past are considered a good predictor of future seismicity. Random earthquakes suggest a Poisson process. If the source zone does not follow a Poisson process then the resulting PSHA might not be valid. The tectonics of a region will effect its spatial distributions. Earthquakes occurring on a single fault, or uniformly distributed, or clustered or random will each have a distinctive spatial distribution. Here we describe a method for both identifying and delineating earthquake clusters and then characterising them. We divide the region into N cells and by counting the number of earthquakes in each cell we obtain a distribution of the number of cells versus the number of earthquakes per cell. This can then be compared to the theoretical Poisson distribution. Areas which deviate from the theoretical Poisson distribution, can then be delineated. This suggests a statistically robust method for determining source zones. Preliminary results suggest that areas of clustering (eg. SWSZ) can also be modelled as a Poisson process which differs from the larger regional Poisson process. The effect of aftershocks and swarms are also investigated.

The inventory of over 200 fault scarps captured in GA's Australian neotectonics database has been used to estimate the maximum magnitude earthquake (Mmax) across the Stable Continental Regions (SCRs) of Australia. This was done by first grouping the scarps according to the spatial divisions described in the recently published neotectonics domain model and calculating the 75th percentile scarp length for each domain. The mean Mmax was then found by averaging the maximum magnitudes predicted from a range of different published relations. Results range between Mw 7.0-7.5±0.2. This suggests that potentially catastrophic earthquakes are possible Australia-wide. These data can form the basis for future seismic hazard assessments, including those for building design codes, both in Australia and analogous SCRs worldwide.

Abstract is too large to be pasted here. See TRIM link: D2011-144613