1. Status and recent updates of the Community Velocity Models (CVM and CVM-H) A. Plesch 1) Define basic structure of these models 2) Highlight their similarities and differences 3) Define viable paths for improvement SCEC provides two alternative velocity models: CVM and CVM-H CVM @ 2000m CVM-H @ 2000m

2. SCEC CVM 4.0 (Magistrale, Day, Clayton, & Graves, 2000, 2005) CVM is a rule-based description of crustal velocity structure… basin velocity descriptions embedded in a regional tomographic (Hauksson, 2000) and 1D background model. Vp is defined at stratigraphic boundaries as a function of depth(Z) and age (T) using Faust’s law: relation is calibrated using well control Vp is linearly interpolated between stratigraphic horizons CVM

3. SCEC CVM 4.0 (Magistrale et al., 2000, 2005) Features of CVM 4.0 representation of most major onshore basins provides top basement and other stratigraphic surfaces that define basin structure Vs and  defined based on relations with Vp. geotechnical layer (GTL); lower Vp and Vs values above 300m in basins based on near-surface soil and sediment types and geotechnical boreholes. CVM 4.0

4. SCEC CVM-H 5.3 (S ü ss, Plesch, & Shaw, 2003, 2007+) CVM-H @ 2000m CVM-H is a data- and geostatistical interpolation-based model of crustal velocity structure… consists of basin velocity descriptions embedded in a regional tomographic model (Hauksson, 2000) Vp is defined based on tens of thousands of direct velocity measurements from industry sonic logs and seismic reflection data employs kriging methods to interpolate basin velocity structures

5. Features of CVM-H representation of major onshore and offshore basins provides top basement surfaces that defines basin structure basins structures are consistent with locations and displacements of major faults in CFM Vs and  defined based on relations with Vp geotechnical layer (CVM-H 5.3); as implemented in CVM 4.0 SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0

6. Features of CVM-H includes lower crust and mantle lower crust tomographic model consistent with basin velocity structure teleseismic and surface wave based mantle model is consistent with crustal model resolution: HR: 250m LR: 1000m CM: 10000m SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0

7. updates since 2007 annual meeting 1D background down to 33km change to Brocher, 2005 for Vp/Vs relation in basins removal of some local interpolation artefacts with velocities from similar locations Vs from models in lower crust, mantle SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0

8. CVM-H 4.0 @+200m SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+)

9. CVM-H 4.0 @ sea level SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+)

10. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -500m

11. SCEC CVM-H 4.0 & 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -1000m

12. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -2000m

13. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -4000m

14. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -6000m

15. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -15000m

16. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -20000m

17. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -20000m

18. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -32000m

19. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -34000m

20. SCEC CVM-H 5.3 (S ü ss et al., 2003, 2007+) CVM-H 4.0 @ -50000m

21. What are similarities and differences in these models? Basin structures both models include most major onshore basins. - Los Angeles - Ventura/San Fernando - Salton trough - … CVM @ 2000m CVM-H @ 2000m

22. What are similarities and differences in these models? Basin structures models have broadly similar average velocity functions … CVM-H CVM Vp (CVM-H 5) Vp (CVM 4)

23. What are similarities and differences in these models? Basin structures CVM-H includes offshore basins and Santa Maria basin CVM-H @ -1000m CVM @ -1000m

24. Basin structures CVM has layers with constant velocity gradients CVM-H has more complex velocity structures within basins. What are similarities and differences in these models? CVM-H CVM

25. Süss & Shaw (2003, 2005) CVM-H 4 & 5 include positions and offsets of major faults represented in the CFM w/ faults w/o faults What are similarities and differences in these models? CVM-H (LA basin)

26. Future SCEC CVM-H Geotechnical layer Provide unlimited resolution GTL by standalone code extracted from the CVM Fortran code. Employ shallow horizons imaged in seismic reflection data to define the base and internal stratification of a new GTL. Los Angeles basin

27. Request from the USR Focus Group… encourage user community to employ the latest models that are best suited to their needs … help us to define ways that models can be improved based on your experiences in using them. How to feed back model perturbation results ? establish an approach for delivering revised models based on 3D waveform inversion approaches. CVM @ 2000m CVM-H @ 2000m