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

2. 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 (Weaver, 2005)

3. Ambient Noise Processing for empirical Green’s functions time (s) 0250100200 4 – 10 sec 10 – 20 sec 20 – 35 sec Broadband time (s) 16 Month Stack Station Y12C Station 109C Normalized velocity Distance: 258 km

4. period (s) U (km/s) Rayleigh group velocities

5. Rayleigh Wave Group Velocity, 8-sec

6. Rayleigh Wave Phase Velocity Maps 477 stations (USArray TA and regional networks) – 0.5 degree grid > 100,000 inter-station paths Ability to improve local resolution with higher density arrays http://ciei.colorado.edu/~morganm

7. Local Dispersion curves for inversion Period (s) Rayleigh wave phase velocity maps Love wave phase velocity maps Period (s) c (km/s), Love c (km/s), Rayleigh

8. Neighbourhood Algorithm to define an ensemble of acceptable models Period (s) c (km/s), Love c (km/s), Rayleigh

9. Crustal thickness estimates Crustal thickness (km)

10. Upper and middle crust slices

11. Lower crust and upper mantle slices

12. Rayleigh waveform comparisons – validation of the USGS Bay Area 3-D Velocity Model (from collaboration with Rodgers and Petersson, LLNL.) BKS-MNRCBKS-BNLO red: EGF green: synthetic

13. 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.

14. Rayleigh wave dispersion measurements period (s) Velocity (km/s) period (s) Group velocitiesPhase velocities BKS - MNRC period (s) Velocity (km/s) period (s) Group velocitiesPhase velocities BKS - BNLO

15. Rayleigh wave 10-sec difference map Group velocityPhase velocity

16. Conclusions and Future Work  Empirical Green’s 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.