New Results from WOMBAT: an Ongoing Program of Passive Seismic Array Deployment in Australia
Abstract
The WOMBAT experiment is an ambitious program of rolling passive seismic array deployments designed to cover a significant portion of the Australian continent. Over the last decade, ~450 sites have been occupied in southeast Australia during the course of 11 separate deployments lasting up to one year. In each case, short period seismometers with a natural frequency of 1 Hz are deployed with spacing varying between 15 and 50 km. The large volume of recorded data is ideal for various classes of study, including teleseismic tomography, crustal receiver functions, ambient noise tomography and array seismology (e.g. probing fine scale core structure). In this presentation, a variety of new results from WOMBAT will be presented. These include (1) joint passive and active source tomography of the Tasmanian lithosphere; (2) combined array teleseismic tomography from the mainland; and (3) ambient noise tomography from multiple arrays. A limitation of conventional teleseismic tomography is that crustal structure is usually poorly resolved, which requires mitigation via station correction terms or the inclusion of a priori structure. In Tasmania, both teleseismic data from WOMBAT and 3-D wide-angle data from a previous experiment are available, a combination which promises good resolution throughout the full lithospheric thickness. We simultaneously invert both passive and active source data for the 3-D structure of the Tasmanian lithosphere, and show that there is little evidence for Tasmania comprising two continental fragments that were juxtaposed during the Phanerozoic. To date, teleseismic data from five mainland arrays that span much of Victoria, southern NSW and eastern South Australia have been combined in a single inversion for 3-D P-wavespeed. The resulting model contains many well resolved features, but the most pronounced is a strong velocity contrast between the Proterozoic lithosphere that underpins the Delamarian Orogen in the west and the Proterozoic lithosphere beneath the Lachlan Orogen in the east. Rayleigh wave group velocity maps of the mid-upper crust derived from ambient noise tomography reveal significant variations in wavespeed near the edges of the Murray Basin, but show little evidence for a transition between the two orogens at shallow depths.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.S22A..03R
- Keywords:
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- 7205 Continental crust (1219);
- 7207 Core (1212;
- 1213;
- 8124);
- 7218 Lithosphere (1236);
- 7270 Tomography (6982;
- 8180)