A Synthesis of Local, Teleseismic, and Ambient Noise Data for High-Resolution Models of Seismic Structure in Western and Southeast Australia
Abstract
Group and phase velocity maps of the Tasmanian and Western Australian lithosphere are obtained through the cross-correlation of seismic ambient noise recorded by temporary array deployments. Group velocities of fundamental mode Rayleigh waves are calculated through an automated frequency-time (FTAN) procedure. Phase-matched filters are applied to the negative time derivative of the symmetric component of the cross-correlation of ambient noise between two stations. Phase velocity maps are derived from the far-field representation of the Green's functions, and the phase ambiguity is resolved through analysis of the observed phase move-out. Group and phase velocities are mapped using an iterative non-linear inversion technique, which smoothly interpolates velocities between a grid of nodes using cubic B-splines. 3-D shear wave velocity can be readily obtained from the phase velocity maps. Additional constraints from receiver functions have the potential to improve depth resolution. The southeast Australia dataset comes from the WOMBAT rolling seismic array project in Tasmania, which in the last decade has seen over 500 stations deployed. Here, we use the 40 station SETA array, which was deployed in southeast Tasmania during 2006 and 2007 and has a station spacing of just 20km. Group and phase velocity maps for this area reinforce results from previous wide-angle tomography studies and clearly discriminate between regions of hard rock and sediment. One of the prominent features of the maps is a pronounced low velocity lineation that coincides with the Tasman conductivity anomaly, a region of elevated conductivity and heat flow, which may reflect the presence of a lithospheric boundary. These methods were also applied to the 20 CAPRAL stations in western Australia. While station spacing is sparser in this case, the greater interstation distances enable longer period dispersion maps to be resolved. The final shear velocity crust models obtained through the joint inversion of dispersion and receiver functions show good agreement with major geological provinces in western Australia. Significant improvement in fit between synthetic and regional earthquake waveforms is evident after the shear velocity models of the crust replace those of the earth reference model ak135. Moreover, reliable shear velocity maps are crucial to the accurate full waveform inversion of regional earthquake seismic moment tensors, as is demonstrated in this study with the 2007 Shark’s Bay event.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.S33A2056Y
- Keywords:
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- 7218 SEISMOLOGY / Lithosphere;
- 7270 SEISMOLOGY / Tomography