Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Stations on the Australian continent receive a rich mixture of ambient seismic noise from the surrounding oceans and the numerous small earthquakes in the earthquakes belts to the north in Indonesia and east in Tonga-Kermadec as well as more distant source zones. The noise field at a station contains information about the structure in the vicinity of the site and this can be exploited by applying an autocorrelation procedure to continuous records. Continuous vertical component records from 242 stations (permanent and temporary) across the continent have been processed using running windows of 6 hours long with subsequent stacking. A distinctive pulse, with a time delay between 8 and 30 s from zero offset, is found in the autocorrelation results. This pulse has a frequency content between 1.5 and 3 Hz suggesting P-wave multiples trapped in the crust. Synthetic modeling, with control of multiple phases, shows that a local PmP phase can be recovered with the autocorrelation method. We are therefore able to use this identification to map out the depth to Moho across the continent, and obtain results that largely conform to those from previous studies using a combination of data from refraction, reflection profiles and receiver functions. This approach can be used for Moho depth estimation using just vertical component records and effective results can be obtained with temporary deployments of just a few months.

Recent earthquake disasters in Indonesia, such as the 2006 Yogyakarta (Mw 6.3, 5749 deaths) and the 2009 Padang (Mw 7.5, over 1100 deaths) earthquakes, together with a long history of earthquake occurrence suggesting the potential for even more lethal disasters in the future, highlight an urgent need for measures to reduce earthquake fatalities. Better land use planning, emergency management training based on credible earthquake scenarios, and improved building codes are all effective means for reducing earthquake fatalities, but these all need to be underpinned by a reliable earthquake hazard assessment. Moreover, a robust and sustainable process for periodically updating such assessments is needed in order to keep pace with developments in Indonesian geology and seismology that are rapidly improving the level of knowledge of earthquake occurrence and the propagation of seismic waves.

This booklet is an update of Earthquakes in the Canberra Region published by the Australian Geological Survey Organisation (AGSO, now Geoscience Australia) and the ACT Emergency Services Bureau in 1996. As 10 years have passed since the previous booklet was published, it was considered appropriate to produce an updated version which includes the more recent earthquake activity in the ACT and surrounding region. Postage and handling costs will be charged for distribution of this product.

A recent passive seismic survey to investigate the variations in crustal structure across the Yilgarn craton has shown significant contrasts in seismic models between neighbouring terranes/superterranes. The Eastern Goldfields showed a unique variability in crustal structure in agreement with a recent reinterpretation of terrane boundaries within the Yilgarn craton. We further investigate the Eastern Goldfields region using a 3-way approach which combines conventional passive seismic analysis with innovative seismic noise-correlation methods and constraints from active source data. The conventional passive seismic analysis enables the receiver function S-velocity structure, and hence composition, of the lower crust to be constrained. The noise-correlation analysis allows seismic model in the 5-15 km depth range to be determined and provides medium resolution coverage across regions not previously explored using active seismic methods. Where active source data have been acquired, shallow structure and deeper seismic velocity determinations are added, providing an unprecedented combination of seismic constraints on the structure of this complex and economically important region. We find that, although some individual terrane boundaries within the new Eastern Goldfields reinterpretation are open to question, the concept of the multi-terrane amalgamation is substantially justified by the exceptional variability of the lower crustal structure. Upper crustal structure is often characterised by seismic discontinuities which may represent detachment surfaces or layered structure that varies between terranes over a sub-100 km length scale. The accretionary history of the superterrane and associated regional tectonic setting of numerous formations of economic significance would now appear to be beyond question.