CVM-SI

Overview

CVM-SCEC Improved (CVM-SI), is a 3D seismic velocity model based upon original CVM-S with changes made based on full 3D tomography inversion results.

In the current implementation of CVM-SI, the CVM-SI software combines material properties from the starting CVM-S model, with CVM-S perturbations that are a result of iterations of inversion simulations by Chen et al (2011) and Lee et al (2010).

The CVMSI query program combines the CVM-S starting model with perturbations. The goal of our cvmsi_query model is to generate high resolution velocity meshes (<100m mesh spacing) using low resolution perturbation model (500m).

Results from CVM-SI20

The following plots compare Vs profiles from 0 - 50km for the starting model and the CVM-SI20 final model for five sites in California.

• USC
• DLA
• PASC
• SVD
• PERRIS

• Profile Sites in KML format

Perturbation Models

The model is expressed as a 3D grid of 1536 x 992 x 100 cells with a grid spacing of 500 m. Query points are smoothed by interpolating the surrounding eight grid points. The four corners of the model region are:

  -116.00000000000000        30.449999999999999     
  -122.30000000000000        34.783499999999997     
  -118.94748257396012        38.303452459152524     
  -112.51822905852465        33.781862621842393     
  -116.00000000000000        30.449999999999999

The map projection is a UTM zone 11 projection. The velocity model is C/Fortran code and associated files that are downloaded, compiled, and run locally. The user queries the models by creating an input file of latitude, longitude, and depth values, and the model returns Vp, Vs, and density at each of those points. This improved model has been imported into UCVM and is referenced with the model label "cvmsi".

Iteration 20 Perturbations

The VP and VP perturbation results are posted the USC computer under: ~pochen/SC_F3DT_dV_SI20/

The perturbations are separated into few files:

CVM4SI20_dV_# : # from 001~100 for perturbations at different depths

The file format is:

column 1: X
column 2: Y
column 3: Z
column 4: longitude
column 5: latitude
column 6: depth (m)  ; 0 is surface
column 7: dVP  (m/sec) ; VP of CVM4SI20 - VP of CVM4
column 8: dVS  (m/sec) ; VS of CVM4SI20 - VS of CVM4

Attached a figure of waveform comparisons for Chino Hills event. In the figure, the black lines are data waveforms and the red lines are synthetic waveforms generated based on our current model. We have applied a six-pole Butterworth filter with corners at 0.02 and 0.2 Hz to both waveforms.

Few more iterations by using the scattering-integral and LSQR algorithms on the Mira. We will let you know, once we have a new model.

Download CVM-SI

CVM-SI may be checked out from SVN with these commands:

svn co https://source.usc.edu/svn/cvmsi/trunk

An UCVM distribution is available for download here UCVM.

References

1. Lee, E., Chen, P., Jordan, T., & Wang, L., 2011. Rapid full‐wave centroid moment tensor (CMT) inversion in a three‐dimensional earth structure model for earthquakes in Southern California, Geophysical Journal International, 186, 311–330.
2. Chen, P., Lee, E., Jordan, T. H., Maechling, P. J., Denolle, M., & Beroza, G. C., 2011, Full-3D Waveform Tomography for Southern California, 2011 SSA Annual Meeting, Memphis, TN
3. Lee, E., Chen, P., Jordan, T. H., Maechling, P. J., Denolle, M., & Beroza, G. C., 2010, Full-3D Waveform Tomography for Southern California, 2010 AGU Fall Meeting, San Francisco, CA

Related Entries

• Community Velocity Model
• CVM-SI Inversion Models