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| Titel |
The Crustal Structure of Australian Continent from Seismic Ambient Noise |
| VerfasserIn |
Erdinc Saygin, Brian Kennett |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250049324
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| Zusammenfassung |
| The use of Green’s function retrieved from seismic ambient noise has become an important
tool to image Earth’s structure on multiple scales during recent years. Because this technique
does not rely on local earthquake signals, it is an excellent tool for the seismological
investigations of Australian continent, where the number and recurrence of earthquakes are
limited.
We use seismic ambient noise to image the Australian Crust including the depth to Moho
by using over 250 broadband stations, which have been deployed during the last 18
years by Research School of Earth Sciences-ANU and Geoscience Australia across
Australian continent. The continuously recorded data from these stations are utilised
to extract the Green’s functions from the ambient seismic noise field. Instead of
using conventional cross-correlation approach, a transfer function method is used,
which has the same phase response with cross-correlation but a broader frequency
response. The interstation dispersion curves of Green’s functions of Rayleigh and
Love wave are estimated with multiple filter analysis. The interstation traveltimes
estimated from filtering are used in nonlinear iterative tomographic approach with
cell size of 1°Ã 1° to create the group velocity dispersion maps for each of the
period.
We then sample Rayleigh group velocity maps for every point to create an associated 1-D
group velocity profile. We also incorporate the finite frequency effects of the wave
propagation by not just only sampling one point but also taking account into the effects of the
neighbouring points. Each of the group velocity profiles is inverted to create a pseudo 3-D
shear wave velocity field of the continent. The inversion is carried with a nonlinear direct
search algorithm, where inversion constraints are imposed from number of other
seismological data such as the sediment thickness to constrain the results. The resultant shear
wave velocity maps are then compared with a recently compiled Moho map of Australian
continent from seismic reflection and receiver function methods. The results agree with the
known tectonic and geological features such as sedimentary basins, Precambrian
blocks. The Moho depth structure derived from 1-D inversion show correlations
with the Moho map estimated from the other seismic techniques. The inversions
carried out with the sediment thickness and Moho depth constraints also give an
accurate representation of the shear wave velocity structure of the mid-crust of the
continent, where the propagation ambient seismic noise is much more dominant. |
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