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Application of empirical Greens functions for
the construction and validation of the GBCVM
Morgan P. Moschetti and Michael H.
Ritzwoller Center for Imaging the Earths
Interior Univ. of Colorado, Boulder Arthur
Rodgers and Anders Petersson Lawrence Livermore
National Laboratory GBCVM Workshop, UNR January
14, 2008
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Overview

• Ambient noise processing for EGFs
• Dispersion measurements for surface wave
  tomography
• 3-D inversion - shear wave velocity values
• Comparison of EGFs and synthetics from the USGS
  Bay Area 3-D velocity model.
• Application to GBCVM

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Ambient Noise Processing for empirical Greens
functions
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Rayleigh group velocities
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Rayleigh Wave Group Velocity, 8-sec
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Rayleigh Wave Phase Velocity Maps

• 477 stations (USArray TA and regional networks)
  0.5 degree grid
• gt 100,000 inter-station paths
• Ability to improve local resolution with higher
  density arrays
• http//ciei.colorado.edu/morganm

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Local Dispersion curves for inversion
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Neighbourhood Algorithm to define an ensemble of
acceptable models
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Crustal thickness estimates
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Upper and middle crust slices
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Lower crust and upper mantle slices
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Rayleigh waveform comparisons validation of the
USGS Bay Area 3-D Velocity Model
(from collaboration with Rodgers and Petersson,
LLNL.)
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Inter-station paths with good measurements

• USGS Bay Area 3-D model two domains
• 130 common paths (EGF/synthetics)
• EGFs limited by stations, synthetics limited by
  model.

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Rayleigh wave dispersion measurements
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Rayleigh wave 10-sec difference map
Group velocity
Phase velocity
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Conclusions and Future Work

• Empirical Greens functions within and across
  Nevada for comparison and inversion.
• Shear-wave velocities across Nevada for
  background values and model/inversion constraint.
• Comparison of EGF and synthetic waveforms allows
  for validation and assimilation of models.
• Improved data coverage from higher density arrays.