Status and recent updates of the Community Velocity Models (CVM and CVM-H)

A. Plesch CVM @ 2000m

SCEC provides two alternative velocity models: CVM and CVM-H

1) Define basic structure of these models 2) Highlight their similarities and differences 3) Define viable paths for improvement CVM-H @ 2000m

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

Features of CVM 4.0

• representation of most major onshore basins

SCEC CVM 4.0

(Magistrale et al., 2000, 2005) CVM 4.0

• provides top basement and other stratigraphic surfaces that define basin structure • Vs and  with Vp.

defined based on relations • geotechnical layer (GTL); lower Vp and Vs values above 300m in basins based on near-surface soil and sediment types and geotechnical boreholes.

SCEC CVM-H 5.3

(S ü ss, Plesch, & Shaw, 2003, 2007+)

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) CVM-H @ 2000m • 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

Features of CVM-H

• representation of major onshore and offshore basins

SCEC CVM-H 5.3

(S ü ss et al., 2003, 2007+) • provides top basement surfaces that defines basin structure CVM-H 4.0

• basins structures are consistent with locations and displacements of major faults in CFM • Vs and  with Vp defined based on relations • geotechnical layer (CVM-H 5.3); as implemented in CVM 4.0

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

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 4.0 & 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

SCEC CVM-H 5.3

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

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

What are similarities and differences in these models?

Basin structures

• models have broadly similar average velocity functions … CVM-H CVM Vp (CVM-H 5)

What are similarities and differences in these models?

CVM @ -1000m

Basin structures

• CVM-H includes offshore basins and Santa Maria basin CVM-H @ -1000m

What are similarities and differences

CVM

in these models?

Basin structures

• CVM has layers with constant velocity gradients • CVM-H has more complex velocity structures within basins. CVM-H

What are similarities and differences in these models?

• CVM-H 4 & 5 include positions and offsets of major faults represented in the CFM

w/ faults w/o faults

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

Request from the USR Focus Group…

• encourage user community to employ the latest models that are best suited to their needs … CVM @ 2000m • 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-H @ 2000m