In the past two years, Geoscience Australia has made significant progress in improving our understanding of earthquake ground-shaking in Australia. This research has culminated in the development of an Australian-specific ground-motion attenuation model and the first national-scale site classification map of Australia. Using a scenario based around the 1989 Newcastle earthquake, we demonstrate how these new products can refine our estimates of ground-shaking in Australia compared to what could be achieved in the recent past. In particular comparisons are drawn against the previous practice of employing ground-motion models derived elsewhere (primarily North America) without any consideration of site response.

On March 6, 2009 a magnitude 4.6 earthquake occurred near Korumburra in southeast Victoria. This event was followed by a series of earthquakes lasting for several months. In the days following this earthquake six temporary high-sample rate seismic recorders were deployed in the epicentral region by Geoscience Australia (GA), Environmental Systems and Services (ES&S) and Gary Gibson. These instruments complemented the permanent networks operated by GA and ES&S, and captured a second large shock on March 18 also measuring 4.6 and many smaller aftershocks.

The ability to provide rapid and accurate estimates of damage following an earthquake is a key priority in seismic risk research, and is central to efficient disaster management. Internationally, several groups are dedicated to achieving these rapid earthquake loss estimates, including SAFER (Seismic eArly warning For EuRope), WAPMERR (World Agency of Planetary Monitoring and Earthquake Risk Reduction) and the automated alarm system 'PAGER' (Prompt Assessment of Global Earthquakes for Response) being developed by the USGS. These agencies aim to provide real-time loss estimates following earthquake events using an empirical approach: historical earthquake data are used to estimate building fragilities, i.e. the relationship between ground shaking intensity and observed structural damage to buildings, which are then used in conjunction with maps of shaking intensity (shake maps) to provide loss estimates. In Australia, this approach is not practicable as there are few historical examples of large, damaging earthquakes in populated areas that can be used as benchmarks for loss estimates.

The Australian Seismological Report 2012 provides a summary of earthquake activity for Australia for 2012. It also provides a summary of earthquakes of Magnitude 5+ in the Australian region, as well as an summary of magnitude 6+ earthquakes worldwide. It has dedicated state and territory earthquake information including: largest earthquakes in the year; largest earthquakes in the state; and tables detailing all earthquakes detected by Geoscience Australia during the year. There are also contributions from Department for Manufacturing, Innovation, Trade, Resources and Energy (DMITRE) and Environmental Systems & Services (ES&S) describing seismic networks and providing earthquake locations.

A new catalogue of Australian earthquakes has been complied which contains 28000 earthquakes of which 17000 are considered main-shocks. The catalogue is complete for all of Australia above M5.5 since 1910, M5 since 1960, M4 since 1970 and M3.5 since 1980. In southern Australia it is complete above M3.5 since 1965 and M2 since 1980. Due to the generally sparse network the location uncertainty of Australian earthquakes is high with only 60% of contemporary earthquakes being located with an uncertainty of 10 km or less. This percentage will be smaller for earthquakes prior to 1980 with very few earthquakes prior to 1960 being located to within 10km. Most of the well located earthquakes are in the southern areas of the continent. The depth of Australian earthquakes are mostly between 8 and 18 km, except for the southwest corner of the continent where they are shallower than 5 km. Local magnitude scales were developed for Australia around 1990, prior to which the Richter magnitude scale was generally used. However at 600 km, a typical hypo-central distance in Australia, the Richter formula gives an overestimate of the magnitude of around 0.5 units. This results in the catalogues pre and post the early 1990's possibly being discrepant. The seismicity in some areas of Australia including the southeast corner, Adelaide fold belt, and the northwest corner, has been ongoing at a steady level for at least 100 years. The seismicity in the southwest corner the seismicity jumped by at least six in the 1940s and has been ongoing since then. The seismicity of much of the rest of Australia appears to be dominated by episodic seismicity. These episodes are characterised by a period of high activity lasting 1-10 years normally associated with a large (M>6) earthquake. Following the large earthquake there is often a period of moderate activity lasting a few years to a few decades. Preceding and following each episode is a period of low activity lasting 0.1ka to 10ka. The seismicity during this quiet period is more than an order of magnitude lower than during the period of high activity. Using the earthquakes since 1970, in the new catalogue, Frequency-Magnitude relations were calculated. Gutenberg-Richter a and b values were calculated on an 85 km grid of Australia. Using the a and b values maps of the probability of a magnitude 5 or greater event per year were produced and are very similar to the GSHAP map for Australia. The resulting maps were used to define four large (> 20000km2) seismogenic zones. There are also several other small zones, some of which appear reflect recent episodes and others appear to be long lived. The expected number of magnitude 5 or greater, 6 or greater, strain rate and deformation rate is given for the four zones, the remainder of Australia and the whole Australian continent. Combining estimate of strain from seismic, GPS and SLR data suggests compressive deformation across Australia of 0.6?2.0mm per year.

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In this paper we propose a new scaling relation between rupture width and rupture length ( where ß = 2/3) and use this to develop a series of new earthquake rupture scaling relations. By substituting and the displacement relation into the definition of seismic moment ( ), we have developed a series of self-consistent scaling relations between seismic moment, rupture area, length, width and displacement. The relations predict log-linear relationships, the slope of which depends only on ß. This slope has been fixed in the least squares analysis of the available earthquake seismic moment, rupture area, length, width, and displacement datasets. These new scaling relations, unlike previous relations, are self-consistent, in that they enable moment, rupture length, width, area and displacement to be estimated from each other and with these estimates all being consistent with the definition of seismic moment. The relations have only two variables, C1 and C2 that have been derived empirically. C1 depends on the size at which a rupture transitions from having a constant aspect ratio to following a power law. C2 depends on the displacement for a given area and so static stress drop. It is likely that these variables differ between tectonic environments and this might explain much of the scatter in the empirical data. Other displacement models, such as and , are also consistent with the empirical data but are not be consistent with MW 2/3logM0, since M0 is not then proportional to A3/2.

Legacy product - no abstract available

Legacy product - no abstract available

Australia is not on the edge of a tectonic plate so why do we have earthquakes? The Indian-Australian plate is being pushed north and is colliding with the Eurasian, Philippine and Pacific plates. This causes stresses to build up in the interior of the plate which is released during earthquakes.