HR: 0800h
AN: S11B-0566    [Abstracts]
TI: Detailed Seismic Imaging of the Australian Lithosphere Using a Dense Rolling Array of Seismometers
AU: Rawlinson, N
EM: nick@rses.anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
AU: Kennett, B
AF: Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
AU: * Tkalcic, H
AF: Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia
AB: Over the last decade, a rolling array of seismometers has been sequentially deployed throughout southeast Australia to record passive seismic activity. To date, nearly 350 separate sites have been occupied with nominal station spacings of 40-50 km on the mainland and 15-20 km in Tasmania. Deployment periods for each of the eight arrays installed so far have varied between 4-10 months, and the number of simultaneously recording instruments has ranged between 20-80. The majority of seismic sensors used have been vertical component short periods, although a number of arrays included a mix of short period and three component broadband instruments. Since October 2006, all arrays contain only three component stations due to an upgrade of the short period seismometer pool. The next deployment of 50 instruments, scheduled for late November 2007, will bring the cumulative array size to nearly 400 seismometers. The intra-plate location of the Australian land mass does not readily permit detailed seismic imaging with local earthquakes. However, the frequency and distribution of large earthquakes associated with the surrounding plate boundary regions makes teleseismic tomography an ideal tool for mapping the 3-D wavespeed structure of the crust and upper mantle beneath the seismic array cluster. So far, four separate teleseismic tomography studies have been published using data from different locations. These results have yielded valuable insight into the architecture of the Australian plate. For example, the possible presence of sizable fragments of Proterozoic continental lithosphere beneath the Paleozoic Lachlan Orogen in eastern Australia; and evidence of a diffuse mantle source for the late Tertiary and Quaternary volcanism in Victoria. The shear volume and diversity of passive seismic data recorded in southeast Australia by the rolling array of seismometers makes it a valuable resource for other classes of study, including ambient noise tomography, shallow receiver functions (using the three-component data), and array seismology (e.g. illumination of the core- mantle boundary). One current line of research aims to combine teleseismic data from all arrays in a single inversion for a unified image of the 3-D structure beneath southeast Australia.
DE: 7218 Lithosphere (1236)
DE: 7270 Tomography (6982, 8180)
DE: 7290 Computational seismology
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 8102 Continental contractional orogenic belts and inversion tectonics
SC: Seismology [S]
MN: 2007 Fall Meeting