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| Titel |
Seismic Anisotropy near Hawaii - Evidence for plume-related mantle flow |
| VerfasserIn |
Gabi Laske, Rachel Marzen |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250129411
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| Publikation (Nr.) |
 EGU/EGU2016-9520.pdf |
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| Zusammenfassung |
| During the Hawaiian PLUME (Plume-Lithosphere Undersea Melt Experiment) deployment,
we collected continuous seismic data at ten land stations and nearly 70 ocean bottom sites
from 2005 through mid-2007. Both the usage broad-band seismometers as well as the central
location of Hawaii with good azimuthal seismicity coverage has allowed us to conduct a
comprehensive analysis of surface wave azimuthal anisotropy at periods between 20 and 100
s. We use a sub-array approach to successively fit propagating spherical wave fronts in order
to obtain frequency-dependent estimates at a large number of points. We use the
standard Smith-and-Dahlen parameterization to express azimuthal variations. A
systematic comparison between results obtained for different truncation levels in the
trigonometric expansion allows us to assess stability of the results and assign error
bars.
At short periods, the fast direction aligns coherently with the fossil spreading direction
across the entire PLUME network. This result supports the idea that flow-aligned
asthenospheric material is "frozen" to the bottom of the cooling plate as it thickens. However,
at longer periods, that sense the asthenosphere below the fast direction rotates incoherently,
indicating that flow in the asthenosphere is significantly perturbed from the direction of
current plate motion. A published shear-wave splitting study (Collins et al., 2012) found
no evidence for such an anomalous mantle flow and therefore seems inconsistent
with our results. We present initial surface-wave inversion results that suggest that
plume-related mantle flow does not reach into the upper lithosphere. We also present
forward-modeling results attempting to reconcile both surface-wave and shear-wave splitting
observations.
Collins, J.A., Wolfe, C.J. and Laske, G., 2012. Shear wave splitting at the Hawaiian hots
pot from the PLUME land and ocean bottom seismometer deployments, Geochem. Geophys.
Geosys., 13, doi:10.1029/2011gc003881. |
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