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  • We report four lessons from experience gained in applying the multiple-mode spatially-averaged coherency method (MMSPAC) at 25 sites in Newcastle (NSW) for the purpose of establishing shear-wave velocity profiles as part of an earthquake hazard study. The MMSPAC technique is logistically viable for use in urban and suburban areas, both on grass sports fields and parks, and on footpaths and roads. A set of seven earthquake-type recording systems and team of three personnel is sufficient to survey three sites per day. The uncertainties of local noise sources from adjacent road traffic or from service pipes contribute to loss of low-frequency SPAC data in a way which is difficult to predict in survey design. Coherencies between individual pairs of sensors should be studied as a quality-control measure with a view to excluding noise-affected sensors prior to interpretation; useful data can still be obtained at a site where one sensor is excluded. The combined use of both SPAC data and HVSR data in inversion and interpretation is a requirement in order to make effective use of low frequency data (typically 0.5 to 2 Hz at these sites) and thus resolve shear-wave velocities in basement rock below 20 to 50 m of soft transported sediments.

  • An optimal combination of geological, geomorphological and climatic properties, along with its high level of contemporary seismicity, makes the Archean craton in the SW corner of Australia an excellent natural laboratory for studying earthquake behaviour in stable continental regions (SCR). Analysis of the palaeo-seismic data derived from 35+ palaeo-earthquake scarps suggests that the long-term seismicity rate is a tenth of the contemporary rate. A 50 site regional GPS/Geodetic network was occupied over the 200 x 400 km study area in 2002 and 2006. Analysis of this data suggests that the long term tectonic strain-rate is about a one seventh (with an uncertainty range of half to a hundredth) of the rate derived from the seismicity recorded over the past 60 years. Re-occupation of this network in 2012 and reprocessing of the 2002 and 2006 data, using updated techniques, should reduce the uncertainty range. The difference between the contemporary seismicity and that suggested by the geological and geodetic data is strong evidence for an episodic (or non-stationary) model of seismicity in non-extended cratonic SCC. By contrast, the Mt Lofty/Flinders Ranges region in South Australia may be exhibiting stationary seismicity behaviour. The geologic structure of this region originally formed in an extensional setting in the Precambrian, and was reactivated in compression in the Cambrian (ca. 500 Ma.) and under the current the current stress field (since ~10-5 ma.). A 50 site GPS/Geodetic network was established in the Flinders ranges in 2003 and reoccupied in 2012. The strain-rate estimated from this data is expected to answer the key question of: Whether the geodetic strain-rate is consistent with the contemporary seismicity (and palaeo-seismicity) in this region or not. Consistency would suggest that the seismicity in this non-extended SCR is stationary, and should be described by a different seismo-tectonic model than the non-extended cratonic SCR

  • Geoscience Australia in collaboration with the Geological Survey of Western Australia conducted a seismic testing program on the Eucla Basin carbonate sediments during May 2012, during a survey to collect deep seismic data across the western Eucla Basin. These data were collected as part of the Albany-Fraser Seismic Survey that consists of three traverses in south-east Western Australia with a total length of 671 km. The major aim of this survey was to image the basement relationship between the Yilgarn craton, the Albany-Fraser zone, and basement rocks further east. Much of this eastern area is covered by the limestones of the Eucla Basin, and there has been little seismic data acquired in this area. These tests were required to confirm the feasibility of collecting deep seismic data beneath the limestones through the region. Geoscience Australia has had little success in penetrating the limestones of the Eucla Basin in previous surveys. Several sets of recording parameters were tested, including 10 Hz geophones and lower frequency 4.5 Hz geophones as parallel spreads. Also, linear upsweeps were compared to low-dwell non-linear upsweeps designed to introduce more low frequency energy into the signal. Initial results from the testing program were encouraging. Production data were subsequently collected along the Trans Australia Railway access road as far as Haig, using Geoscience Australia's standard deep crustal seismic acquisition parameters.

  • Processed seismic data (SEG-Y format) and TIFF images for the 2007 AuScope Deep Crustal Seismic Survey (L186), acquired by Geoscience Australia (GA) and funded by the Australian Government under the National Collaborative Research Infrastructure Strategy. Field logistics and processing were carried out by the Seismic Acquisition and Processing team from Geoscience Australia. Stack and migrated data for line 07GA-A1 as well as CDP coordinates. The seismic line is oriented approximately northeast-southwest and extends from near Mt Surprise in the southwest to near Mareeba in the northeast. Raw data for this survey are available on request from clientservices@ga.gov.au